feat(ui): persist_state window/buffer persistence

[jensenojs]

When ui.persist_state = true (default), toggle hides windows without deleting buffers and restores them on next toggle, preserving input draft content, scroll/cursor position, focused pane, and input_hidden state.

Three-state window model:
closed → visible → hidden → visible
↑___________↓____________↑
(teardown) (restore)

Decision engine resolves (status, persist_state, has_display_route, in_tab) → action:

#	status	in_tab	persist_state	has_display_route	action
1	hidden	any	true	any	restore_hidden
2	hidden	any	false	any	close_hidden
3	visible	false	any	any	migrate
4	visible	true	any	true	close
5	visible	true	false	any	close
6	visible	true	true	false	hide
7	closed	any	any	any	open

Note: Multiple opencode instances across tabs are not currently supported.

[jensenojs]

TODO : A complete video demonstration is needed to show the effects after merging my three pull requests

iShot_2026-02-15_09.33.20.mp4

benchmark

If you have any suggestions regarding code maintainability, please don't hesitate to point them out, as this is very helpful for my growth and the maintenance of the code.

Nevertheless, I would prefer to complete it further in subsequent PRs. The current split is making me a bit exhausted.

[sudo-tee]

@jensenojs

Is this MR ready to re-review ?

There is some conflicts at the moment against main.

[jensenojs]

yes, The core is implementing the persist_state tri-state model (closed/hidden/visible) + decision-driven toggle logic.

Major Changes (4 Files)

File	Changes	Core Content
state.lua	+304/-13	Added OpencodeHiddenBuffers type, OpencodeToggleDecision type, decision logic resolve_toggle_decision, window state management methods
ui.lua	+276/-29	Hide/restore window lifecycle, cursor position snapshot/restore, close_windows_impl unifies teardown vs hide handling
api.lua	+84/-21	toggle() completely refactored to decision-table pattern, added hide() API, uses state.resolve_toggle_decision()
core.lua	+59/-39	M.open() supports restore_hidden flow, multiple state.windows → state.is_visible() replacements

Actually, the close_windows_impl function is a bit messy because the specific logic for hide and close is coupled with the common logic. I'm considering cleaning it up to make it more streamlined later on.

Secondary Changes (Adaptation Adjustments)

File	Changes	Description
tests/unit/persist_state_spec.lua	+678	New test file (largest line count)
input/output_window.lua	+12/-4	Cursor tracking migrated to new API (get_window_cursor + set_cursor_position)
footer.lua	+5/-2	Added preserve_buffer parameter support
cursor_tracking_spec.lua	+9/-6	Tests adapted to new function names
input_window.lua	+4/-0	Added cursor position save in _hide() for auto_hide scenario
7 other files	minor	README, config, types, autocmds, renderer, etc.

Thanks for your hard work (both you and me). I definitely won't take on such a big PR again. I would rather bother you a few more times. @sudo-tee

[sudo-tee]

I tested a bit and it works well, I like it overall

I left a couple of comments regarding the structure of the code as this is quite complex.

I feel like this should be simplified a little bit before merging.

Thanks a lot for your efforts on this.

It's almost there :)

[sudo-tee]

@jensenojs

Thanks for addressing the comments I made.

It definitely is easier to understand this way.

I will do a final testing this weekend and it should be good to go