feat(lint): E003 scope-precise binding sets + did-you-mean (#404 increment two)

[InauguralPhysicist]

Part of #404 (issue stays open — path-precise analysis and token-precise LSP ranges remain).

What

E003's binding sets go from whole-file over-approximation to scope-precise (still path-insensitive), and undefined-name messages gain an edit-distance-1 did-you-mean suggestion.

New true-positive classes — each one is a program the runtime rejects with undefined variable:

• sibling/module reads of a function-local (fresh-name is or local)
• module calls of a nested define (enclosing-local by the runtime's rules)
• post-loop reads of a module-level for variable (the VM loop-scopes it — the same divergence class ouroboros PR Update self-hosting quickstart to reflect bootstrap success #79 hit; function-level for-vars survive, and the lint matches)

Method

Every scope rule was pinned empirically against the interpreter first (10 probe programs), then implemented: closures read enclosing scopes, module names are order-insensitive, listcomp vars leak to the containing scope, catch vars bind in the containing scope. The scope chain literally is the runtime's Env parent chain; COLLECT creates one Env per scope-introducing node in walk order and FLAG replays them by counter — the two walks visit identical nodes in identical order by construction.

External contributions (load_file targets, # lint: loaded-by composers) deliberately stay a flat over-approximation: scope-narrowing someone else's file buys precision nobody asked for at real false-positive risk.

Suggestions are distance-1 only, names ≥ 3 chars — near-certain or absent: undefined name 'totl' — no binding on any path (did you mean 'total'?)

Verification

• Calibration gate: zero E003 across lib/ + examples/ + tests/ and ALL 10 consumer repos (one FP breaks consumer CI — the gate is the contract)
• test_lint.sh 72/72 — 4 new firing fixtures + a runtime-verified silent fixture (runs clean under the interpreter, exit 0)
• Full suite 2609/2609 release AND ASan+UBSan detect_leaks=1, leak tally 0
• LSP 67/67 + test_lsp_asan.sh clean — the LSP shares the pass and inherits the precision
• Existing E003 fixtures unchanged and passing (suggestion suffix is additive)

Also fixes a stale DIAGNOSTICS.md sentence left by #406 (the E100 note still described catch binding the error string).

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