v0.1.19 — precision pass + codegraph benchmark

Fixed

• Rust extractor precision raised from 67% → 99.8% recall via 4 additive
  queries.scm patterns (dogfood-found 2026-06-04 by indexing the Mycelium
  repo against itself and comparing per-file symbol counts vs ground truth):

  • trait T { fn x(); } trait method signatures are now captured
    (previously only trait T was indexed; T::x was silently dropped —
    e.g. FileReindexer::reindex was invisible while every impl FileReindexer for X method was present).
  • trait T { fn x() {...} } trait default-method bodies captured.
  • Module-level static FOO: ... items captured (previously only const
    — e.g. static PACK_REGISTRY: OnceLock<...> was missing).
  • Associated pub const items inside impl blocks captured (e.g.
    impl NodeId { pub const NULL: Self = ...; }).
  • Functions/structs/consts inside nested mod blocks (notably
    #[cfg(test)] mod tests { fn ... }) now captured at every position
    in the body, not only at head/tail.

  Verified on the Mycelium repo: 70 of 80 Rust files now match ground-truth
  symbol counts exactly (was 44 of 80). Total recall 99.8% (2664 / 2668).
  5 RED-first regression tests in crates/mycelium-core/src/extractor/tests.rs.

  Head-to-head vs codegraph 0.9.8 on the same repo: Mycelium index time
  0.32 s vs codegraph 0.93 s (3× faster); Mycelium 70 of 80 files at exact
  ground-truth match vs codegraph 1 of 80 (codegraph over-counts symbols
  by 19.7% — different granularity).

Docs

• ADR-0008: redb as default storage backend (Phase 3 flip decision record). Documents the rationale for switching from InMemoryBackend to RedbBackend as the production default in v0.1.17, prerequisites met (equivalence tests, crash-safety, warm SLA).
• ADR numbering fix: renamed docs/adr/0008-redb-storage-engine.md → docs/adr/0009-redb-storage-engine.md (ADR-0009) to resolve the 0007/0008 slot collision; updated cross-references in rfc-0100-execution-plan.md, rfcs/0104-charter-warm-cold-sla-split.md, and docs/adr/0008-redb-as-default-backend.md.