feat: emit func_name caller-symbol tag (#3422)

[veksen]

Implements the producer half of Query-Doctor/Site#3422: capture the enclosing caller symbol from the same V8 stack frame traceCaller() already parses, and emit it as a new func_name SQLCommenter tag.

Why

Provenance today is file:line:col only. Line/col drift when code above the call site changes, so mapping captured queries back to source against any other revision silently misattributes them (Query-Doctor/Site#3367). The enclosing method symbol (e.g. reactionsRepo.findFavorites) is edit-stable and is the join key that makes captured-query → source-method coverage mapping (Query-Doctor/Site#3418 / Query-Doctor/Site#3419) reliable without checking out the capture's exact commit. func_name is the canonical key other adapters (postgres-tracked-pool) already emit.

What changed

• traceCaller() now returns { file, symbol? } instead of a bare file string. The symbol is parsed from the same frame already selected — no new frame-selection logic.
• New func_name tag emitted when a symbol is present; falls back to file alone when the frame is anonymous / <anonymous> / top-level (never an empty tag). async prefixes are stripped.
• In drizzle, the { file, symbol? } payload is threaded through the 0.4.0 per-query concurrency machinery unchanged — only the payload widened from string.
• Applied to drizzle, mikroorm, and typeorm; each README's emitted-fields table gains the func_name row.

Verification (grounded in real V8 frames, not assumptions)

Probed actual frames first, then asserted:

• named function → loadRow; object method → Object.findFavorites; class method → UserService.list; arrow-assigned const → arrowAssigned.
• anonymous frame → no func_name, file still emitted (the fallback contract).
• concurrency → two queries built before either executes each keep their own symbol.
• serialization: keys sort alphabetically (db_driver, file, func_name, …); asserted file precedes func_name.

All suites pass: drizzle 26, mikroorm 31, typeorm 24 (dual ESM/CJS builds clean).

Versions

• drizzle 0.4.0 → 0.5.0, mikroorm 0.3.0 → 0.4.0, typeorm 0.3.0 → 0.4.0 (new emitted tag; traceCaller's return shape changed, so a minor under 0.x).

Refs: Query-Doctor/Site#3422, Query-Doctor/Site#3367, Query-Doctor/Site#3418, Query-Doctor/Site#3419. The Site consumer (feat-caller-symbol-tag) already renders func_name, so it displays the moment this publishes.

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