fix(extract): count method calls on instanceof-narrowed values as class-member uses

[BartWaardenburg]

DRAFT: Opened because the reviewer returned FIX (not SHIP). One blocking concern must be resolved before merge: bump CACHE_VERSION in crates/extract/src/cache/types.rs from 107 to 108 with a doc-comment paragraph referencing #845 (same pattern used for #752).

Summary

Adds visit_if_statement to the Oxc AST visitor in crates/extract/src/visitor/visit_impl.rs. When an if statement's test contains x instanceof ClassName (or &&-chained variants), the narrowing x -> ClassName is inserted into binding_target_names before the body is walked. The existing resolve_bound_member_accesses finalization pass then re-emits any x.method() call as ClassName.method, crediting the method as used. A standalone collect_instanceof_narrowings helper recurses through LogicalExpression(&&) and ParenthesizedExpression nodes. Two regression tests are added to crates/extract/src/tests/js_ts/member_access.rs.

Review

Verdict: FIX

• BLOCKING: Missing CACHE_VERSION bump. The fix changes emitted member_accesses for any file containing an instanceof guard, and member_accesses is serialized into CachedModule (crates/extract/src/cache/types.rs:203). The cache-version doc comment at types.rs:89-92 records the exact precedent: issue unused-class-members FP: methods called only from Svelte <template> member expressions #752 bumped the version for the structurally identical change. With a warm cache, users upgrading will continue to see the false positive until an unrelated edit forces re-extraction. Bump to 108 with a doc-comment paragraph referencing Method call through instanceof narrowing not counted as a class-member use #845.
• Code fix itself is correct, minimal (2 files, additive), clippy-clean, and fmt-clean. End-to-end validated: getMessage (used only via instanceof-narrowed call) is credited and not reported, while a genuinely-unused sibling method (unusedOne) still reports.
• Tests are a real regression guard: both new tests in member_access.rs fail before the visitor change and pass after.
• An integration-level assertion (analyze verdict, not just extract layer) would be stronger but is not blocking.

Closes #845