perf(resolution): fix O(K²) import-node blowup in "Resolving refs" (#915) (#965)

* perf(resolution): resolve imports to definitions, not sibling import nodes (#915)

"Resolving refs" crawled (tens of minutes) on large projects — most painfully
ones mixing a big front-end and back-end. An external package or module imported
across hundreds/thousands of files (react, a shared UI package, Python
logging/typing) is re-declared as an `import` node in every importing file, so
its unresolved import ref fell through to the exact-name matcher, which scored
all K same-named import nodes via findBestMatch — K refs x K candidates = O(K^2)
per package, producing only meaningless import->import edges.

Fix: exclude `import`-kind nodes as name-match targets (they're statements, not
definitions; real import->definition resolution is the import resolver's job).
Plus two safe constant-factor wins in findBestMatch: hoist the per-candidate
ref.filePath split, and skip cross-language candidates when a same-language one
exists (provably the same winner — same-language scores >=50, cross-language
maxes at 35).

Measured: superset (Py+TS) candidates scored 7.5M -> 833K (9x), non-import edges
preserved (+1618 now resolve to real defs), ~22K useless import->import edges
removed; kubernetes (Go) computePathProximity 37.2s -> 5.0s; synthetic 8k-file
mixed repo (K=4000) resolution 16.0s -> 1.7s. Full suite green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* docs: correct stale better-sqlite3/wasm references to node:sqlite

The SQLite backend has been Node's built-in node:sqlite (real SQLite, WAL + FTS5,
from the bundled runtime) for a while — there is no native build step and no
node-sqlite3-wasm fallback. README and the docs site were already updated; this
catches the stragglers:

- CLAUDE.md: the src/db/ backend description and the sqlite-backend test note.
- src/db/index.ts, src/mcp/tools.ts: two code comments that still blamed "the
  wasm backend" for non-WAL behavior (reworded to "when WAL isn't in effect").

Leaves tree-sitter grammar wasm (web-tree-sitter / --liftoff-only) untouched —
that's a different, still-current use of wasm.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* chore(telemetry): drop the dead sqlite_backend field (schema v2)

node:sqlite is now the only backend, so the `index` event's `sqlite_backend`
field was a constant ("native") carrying no signal — and the `install` event
never actually sent it. Remove the field and the backendKind() helper, bump the
telemetry SCHEMA_VERSION 1 -> 2, and update TELEMETRY.md + docs/design/telemetry.md.

The ingest worker is deliberately left tolerant: `index` doesn't require the
field and schema_version validates as nonNegInt(99), so v2 events ingest fine and
old clients still sending v1 + sqlite_backend keep validating too. Added a legacy
comment there explaining it's safe to drop once old-client share is negligible.

telemetry.test.ts: the assertion pinning schema_version and a stale-claim fixture
line updated 1 -> 2. All telemetry tests pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -50,7 +50,7 @@ The public API surface is `src/index.ts` — the `CodeGraph` class wires all the
 ### Module layout
 
 - `src/index.ts` — `CodeGraph` class: `init`/`open`/`close`, `indexAll`, `sync`, `searchNodes`, `getCallers`/`getCallees`, `getImpactRadius`, `buildContext`, `watch`/`unwatch`.
-- `src/db/` — `DatabaseConnection`, `QueryBuilder` (prepared statements), `schema.sql`. Backed by `better-sqlite3` (native) when available, transparently falls back to `node-sqlite3-wasm`. `codegraph status` surfaces which backend is live; wasm is the slow path.
+- `src/db/` — `DatabaseConnection`, `QueryBuilder` (prepared statements), `schema.sql`, `sqlite-adapter.ts`. Backed by Node's built-in **`node:sqlite`** (`DatabaseSync`) — real SQLite with WAL + FTS5, exposed through a thin better-sqlite3-shaped adapter. The bundled runtime always ships Node ≥22.5, so `node:sqlite` is always available: **no native build step and no wasm fallback**. (Running from source needs Node ≥22.5.) `codegraph status` reports the live backend (`node-sqlite`, the sole backend).
 - `src/extraction/` — `ExtractionOrchestrator`, tree-sitter wrappers, per-language extractors under `languages/` (one file per language), plus standalone extractors for non-tree-sitter formats (`svelte-extractor.ts`, `vue-extractor.ts`, `liquid-extractor.ts`, `dfm-extractor.ts` for Delphi). `parse-worker.ts` runs heavy parsing off the main thread.
 - `src/resolution/` — `ReferenceResolver` orchestrates `import-resolver.ts` (with `path-aliases.ts` for tsconfig path aliases + cargo workspace member globs), `name-matcher.ts`, and `frameworks/` (Express, Laravel, Rails, FastAPI, Django, Flask, Spring, Gin, Axum, ASP.NET, Vapor, React Router, SvelteKit, Vue/Nuxt, Cargo workspaces). Frameworks emit `route` nodes and `references` edges.
 - `src/graph/` — `GraphTraverser` (BFS/DFS, impact radius, path finding) and `GraphQueryManager` (high-level queries).
@@ -163,7 +163,7 @@ Tests live in `__tests__/` and mirror the module they cover. Notable ones beyond
 
 - `installer-targets.test.ts` — parameterized contract suite across all 4 agent targets (see installer notes above).
 - `evaluation/` — `runner.ts` + `test-cases.ts` exercise codegraph against synthetic projects and score the results; run via `npm run eval` (builds first). Not part of `npm test`.
-- `sqlite-backend.test.ts` — covers native + wasm backend selection and fallback.
+- `sqlite-backend.test.ts` / `node-sqlite-backend.test.ts` — pin that `node:sqlite` is the sole backend: `getBackend()` reports `node-sqlite` and the DB comes up in WAL.
 - `pr19-improvements.test.ts`, `frameworks-integration.test.ts` — regression coverage for specific past PRs/incidents; don't rename these, the names anchor to git history.
 
 Tests create temp dirs with `fs.mkdtempSync` and clean up in `afterEach`. They write real files and exercise real SQLite — there is no DB mocking.