fix(runtime): Harden cword updates, pin identity matching, and grep fallback behavior

[mhiro2]

Summary

• make cword debounce updates independent per window so split navigation does not drop pending highlights
• tighten pin identity matching so auto toggle and unpin only act on exact matches and avoid ambiguous
  removals
• prefer rg --vimgrep for quickfix fallback grep, with vimgrep kept as the fallback path when ripgrep is
  unavailable
• allow flash.timeout_ms = 0, align empty-state picker notices, and update the related tests and docs

Changes

• 0817bae : fix(cword): use per-window debounce timers
  • Replaced the shared cword debounce timer with window-local timers so cursor movement in one split no
    longer cancels pending updates in another.
  • Added regression coverage for concurrent cword updates across multiple windows.
• f412256 : fix(state): tighten pin identity matching
  • Changed auto-toggle matching to require an exact raw-and-pattern match so pins with different match
    semantics can coexist.
  • Updated UnpinWord to prefer exact matches and warn instead of deleting an arbitrary slot when the
    current word maps to multiple pins.
  • Added state, command, and auto-allocation tests for the stricter identity rules.
• 1e83005 : fix(grep): prefer rg for quickfix fallback
  • Switched quickfix fallback grep to use rg --vimgrep when available to avoid the broad vimgrep **/*
    scan in large or mixed repositories.
  • Kept the legacy vimgrep path as a fallback for environments without ripgrep and covered both branches
    with tests.
• df85644 : fix(ui): allow zero flash timeout and align empty notices
  • Allowed flash.timeout_ms = 0 so flash highlights can clear on the next event loop tick without failing
    config validation.
  • Standardized empty-state picker notifications to INFO level for a more consistent user-facing experience.
  • Updated help and README text to reflect the revised flash and grep fallback behavior.

[github-actions]

Benchmark Results

nvim --headless -u NONE -c "lua dofile('bench/run.lua')" -c "qa!"

== bench.bench_reapply ==
---------------------------------------------------------------------------------------------
Benchmark                                        Iters    Mean (us)     Min (us)     Max (us)
---------------------------------------------------------------------------------------------
reapply_all  slots=1 wins=1                         50          3.2          0.7         25.2
reapply_all  slots=1 wins=5                         50          6.2          3.3         21.2
reapply_all  slots=1 wins=10                        50         12.5          5.9         47.2
reapply_all  slots=1 wins=20                        50         13.6         11.6         28.6
reapply_all  slots=5 wins=1                         50          1.3          0.7          7.9
reapply_all  slots=5 wins=5                         50          6.2          3.9         14.4
reapply_all  slots=5 wins=10                        50          9.0          7.0         39.5
reapply_all  slots=5 wins=20                        50         16.3         13.7         35.5
reapply_all  slots=9 wins=1                         50          2.8          0.8         10.0
reapply_all  slots=9 wins=5                         50          3.9          3.8          4.2
reapply_all  slots=9 wins=10                        50          8.0          7.7          8.5
reapply_all  slots=9 wins=20                        50         22.9         15.6         78.1
---------------------------------------------------------------------------------------------

== bench.bench_apply ==
---------------------------------------------------------------------------------------------
Benchmark                                        Iters    Mean (us)     Min (us)     Max (us)
---------------------------------------------------------------------------------------------
apply_slot_globally  wins=1                        100          5.1          3.9         25.5
apply_slot_globally  wins=5                        100         21.2         18.9         42.6
apply_slot_globally  wins=10                       100         42.5         37.1         95.6
apply_slot_globally  wins=20                       100         88.5         76.6        167.6
apply_slot_for_window  existing=0                  200          4.0          3.7         24.5
apply_slot_for_window  existing=5                  200          4.4          4.1         26.8
apply_slot_for_window  existing=9                  200          5.0          4.7         29.8
---------------------------------------------------------------------------------------------

== bench.bench_clear ==
---------------------------------------------------------------------------------------------
Benchmark                                        Iters    Mean (us)     Min (us)     Max (us)
---------------------------------------------------------------------------------------------
clear_all_globally  slots=1 wins=1                  30         93.3         56.3        168.2
clear_all_globally  slots=1 wins=5                  30        197.6        157.7        354.5
clear_all_globally  slots=1 wins=10                 30        303.3        261.1        536.7
clear_all_globally  slots=5 wins=1                  30         99.6         81.6        188.6
clear_all_globally  slots=5 wins=5                  30        297.4        259.5        503.6
clear_all_globally  slots=5 wins=10                 30        521.3        458.2        800.9
clear_all_globally  slots=9 wins=1                  30        134.5        109.3        251.2
clear_all_globally  slots=9 wins=5                  30        428.0        363.4        633.8
clear_all_globally  slots=9 wins=10                 30        739.1        660.8       1048.2
---------------------------------------------------------------------------------------------

== bench.bench_set_clear ==
---------------------------------------------------------------------------------------------
Benchmark                                        Iters    Mean (us)     Min (us)     Max (us)
---------------------------------------------------------------------------------------------
set+clear cycle  wins=1                             50         28.2         13.7        101.6
set+clear cycle  wins=5                             50         50.5         36.9         93.6
set+clear cycle  wins=10                            50        119.6         66.7        204.9
---------------------------------------------------------------------------------------------

== bench.bench_jump ==---------------------------------------------------------------------------------------------
Benchmark                                        Iters    Mean (us)     Min (us)     Max (us)
---------------------------------------------------------------------------------------------
jump.next  slots=1                                 100         43.1         19.6        131.9
jump.next  slots=5                                 100       5403.8       5243.5       9938.6
jump.next  slots=9                                 100      15996.3      15664.9      23274.3
---------------------------------------------------------------------------------------------

== bench.bench_cword ==
---------------------------------------------------------------------------------------------
Benchmark                                        Iters    Mean (us)     Min (us)     Max (us)
---------------------------------------------------------------------------------------------
apply_cword_for_window                             200          2.6          2.0         35.3
---------------------------------------------------------------------------------------------

== bench.bench_symbol ==
---------------------------------------------------------------------------------------------
Benchmark                                        Iters    Mean (us)     Min (us)     Max (us)
---------------------------------------------------------------------------------------------
symbol: get_symbol (on identifier)                 200          9.2          4.1         67.5
symbol: get_symbol (on keyword)                    200         14.4          5.5         80.8
symbol: set+clear cycle (source=symbol)             50         27.3         20.5        144.5
symbol: set+clear cycle (source=cword)              50         16.0         13.1         35.2
---------------------------------------------------------------------------------------------

== SUMMARY ==
---------------------------------------------------------------------------------------------
Benchmark                                        Iters    Mean (us)     Min (us)     Max (us)
---------------------------------------------------------------------------------------------
reapply_all  slots=1 wins=1                         50          3.2          0.7         25.2
reapply_all  slots=1 wins=5                         50          6.2          3.3         21.2
reapply_all  slots=1 wins=10                        50         12.5          5.9         47.2
reapply_all  slots=1 wins=20                        50         13.6         11.6         28.6
reapply_all  slots=5 wins=1                         50          1.3          0.7          7.9
reapply_all  slots=5 wins=5                         50          6.2          3.9         14.4
reapply_all  slots=5 wins=10                        50          9.0          7.0         39.5
reapply_all  slots=5 wins=20                        50         16.3         13.7         35.5
reapply_all  slots=9 wins=1                         50          2.8          0.8         10.0
reapply_all  slots=9 wins=5                         50          3.9          3.8          4.2
reapply_all  slots=9 wins=10                        50          8.0          7.7          8.5
reapply_all  slots=9 wins=20                        50         22.9         15.6         78.1
apply_slot_globally  wins=1                        100          5.1          3.9         25.5
apply_slot_globally  wins=5                        100         21.2         18.9         42.6
apply_slot_globally  wins=10                       100         42.5         37.1         95.6
apply_slot_globally  wins=20                       100         88.5         76.6        167.6
apply_slot_for_window  existing=0                  200          4.0          3.7         24.5
apply_slot_for_window  existing=5                  200          4.4          4.1         26.8
apply_slot_for_window  existing=9                  200          5.0          4.7         29.8
clear_all_globally  slots=1 wins=1                  30         93.3         56.3        168.2
clear_all_globally  slots=1 wins=5                  30        197.6        157.7        354.5
clear_all_globally  slots=1 wins=10                 30        303.3        261.1        536.7
clear_all_globally  slots=5 wins=1                  30         99.6         81.6        188.6
clear_all_globally  slots=5 wins=5                  30        297.4        259.5        503.6
clear_all_globally  slots=5 wins=10                 30        521.3        458.2        800.9
clear_all_globally  slots=9 wins=1                  30        134.5        109.3        251.2
clear_all_globally  slots=9 wins=5                  30        428.0        363.4        633.8
clear_all_globally  slots=9 wins=10                 30        739.1        660.8       1048.2
set+clear cycle  wins=1                             50         28.2         13.7        101.6
set+clear cycle  wins=5                             50         50.5         36.9         93.6
set+clear cycle  wins=10                            50        119.6         66.7        204.9
jump.next  slots=1                                 100         43.1         19.6        131.9
jump.next  slots=5                                 100       5403.8       5243.5       9938.6
jump.next  slots=9                                 100      15996.3      15664.9      23274.3
apply_cword_for_window                             200          2.6          2.0         35.3
symbol: get_symbol (on identifier)                 200          9.2          4.1         67.5
symbol: get_symbol (on keyword)                    200         14.4          5.5         80.8
symbol: set+clear cycle (source=symbol)             50         27.3         20.5        144.5
symbol: set+clear cycle (source=cword)              50         16.0         13.1         35.2
---------------------------------------------------------------------------------------------