v0.9.0

## ⚠️ Breaking change — node IDs changed

Node IDs now include the full repo-relative path, fixing silent data loss when same-named files live in different directories. **Existing graphs migrate automatically on the next build/update (no LLM re-bill).** Run `graphify extract --force` to recover nodes that previously collided. If you push to a persisted **Neo4j** store, re-import after upgrading; GraphML/Gephi layouts go stale; query by label rather than persisting node IDs.

- **Breaking — node IDs now include the full repo-relative path** (#1504, #1509). The node-ID stem was the immediate parent dir + filename, so same-named files in different directories collided into one last-writer-wins node and silently dropped graph content (`docs/v1/api/README.md` and `docs/v2/api/README.md` both → `api_readme`). The stem is now the full repo-relative path (`docs_v1_api_readme` vs `docs_v2_api_readme`); top-level files are unchanged (`setup.py` → `setup`). The AST extractor, the LLM system prompt, the extraction-spec, and the two hand-copied stem helpers are all aligned to this one rule (fixing the #1509 AST↔LLM divergence that produced ghost duplicates), and `build_from_json` deterministically re-keys any cached/older semantic fragment onto the new IDs from its `source_file` so the unversioned semantic cache survives without ghosts or a re-bill. **Existing graphs migrate to the new ID format automatically on the next `build`/`update`** (no re-bill). Note: same-named files in different directories that previously collided into one node are only *recovered as distinct nodes* by a fresh extraction — run `graphify extract --force` to rebuild and gain them (migrating an already-collided graph/cache can't resurrect the nodes that were already dropped). If you push to a persisted **Neo4j** store, re-import after upgrading (re-exported IDs change); saved Gephi/yEd (GraphML) layouts go stale; MCP/cypher consumers should query by label rather than persisting node IDs across rebuilds.
- Feat: `--timing` flag on `graphify extract` and `graphify cluster-only` prints per-stage wall-clock timings to stderr (#1490). Shows how long each pipeline stage takes — `extract`: detect → AST → semantic → build → cluster → analyze → export; `cluster-only`: load → cluster → analyze → label → report → export — plus a final total, so slow stages are visible on large corpora. Off by default (monotonic `perf_counter`, stderr-only); machine-read stdout / `graph.json` are unchanged.