[codex] Fix HNSW delete/reinsert rebuild

[joaoh82]

Summary

Fixes SQLR-8: HNSW indexes could panic after rows were deleted and new vectors were inserted within the same open connection.

Root Cause

DELETE / vector-column UPDATE marked HNSW indexes as needs_rebuild, but only the pager save path rebuilt them. In-memory INSERT still appended into the stale graph. Deleted rowids could remain in neighbor lists, and the HNSW get_vec closure returned an empty vector for those stale ids, eventually causing DistanceMetric::compute to assert or index into a zero-length slice.

Changes

• Rebuild dirty HNSW indexes from surviving rows before the next INSERT on an indexed vector column.
• Reuse the same rebuild helper from the pager save path so save/COMMIT behavior stays consistent.
• Change HNSW distance/search/insert paths to return typed SQLRiteErrors for empty or mismatched vector dimensions instead of panicking.
• Add a regression test for DELETE -> INSERT -> KNN query in one connection.
• Remove the examples/nodejs-notes db.reopen() workaround and the known-limitation README entry.
• Update docs/sql-engine.md with the current dirty-index lifecycle.

Validation

• Original REPL reproducer now completes and returns document_id = 2.
• cargo build --workspace --exclude sqlrite-desktop --exclude sqlrite-python --exclude sqlrite-nodejs --exclude sqlrite-benchmarks --all-targets
• cargo test --workspace --exclude sqlrite-desktop --exclude sqlrite-python --exclude sqlrite-nodejs --exclude sqlrite-benchmarks
• cargo test hnsw --lib
• npm test in examples/nodejs-notes
• cargo fmt --all -- --check
• cargo clippy --workspace --exclude sqlrite-desktop --exclude sqlrite-python --exclude sqlrite-nodejs --exclude sqlrite-benchmarks --all-targets (passes with existing warnings)
• cargo doc --workspace --exclude sqlrite-desktop --exclude sqlrite-python --exclude sqlrite-nodejs --exclude sqlrite-benchmarks --no-deps (passes with existing rustdoc warnings)

Deploy Plan

Because this is a process-aborting bug in the engine and affects SDK consumers, ship as a patch release.

1. Merge this PR after CI is green.
2. Cut a patch version with scripts/bump-version.sh 0.10.1.
3. Run the release validation matrix from AGENTS.md, including workspace build/test/clippy/doc and examples/nodejs-notes npm test.
4. Publish release artifacts in dependency order: engine crate, FFI/SDK packages, MCP binary/package, then example docs/site references if applicable.
5. For examples/nodejs-notes, verify the refresh flow no longer performs a close/reopen hop and announce that consumers can remove their own workaround.
6. Add a short release note: "Fix HNSW panic after DELETE followed by INSERT in the same connection; HNSW now rebuilds dirty in-memory graphs before reuse and reports typed dimension errors."

Notes

Unrelated local dirty files were intentionally left out of this PR: an untracked AGENTS.md and a mode-only change on examples/nodejs-notes/bin/sqlrite-notes.mjs.

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Project	Deployment	Actions	Updated (UTC)
rust-sqlite	Ready	Preview, Comment	May 25, 2026 7:48am