v1.34.0 — zero-false-negative enumeration + ops hardening

1.34.0 — zero-false-negative enumeration + ops hardening

Enumeration moved from directory-walking to git ls-files (tracked +
untracked-unignored), with the walker as fallback. This is not just faster —
it is MORE COMPLETE: git knows which files are tracked, and tracked beats
gitignore. Measured on a live monorepo: 26 real docs (SRS, bug
investigations) lived under a docs/* ignore pattern but were committed
anyway — the walker dropped them forever, the git tier indexes them.
Staleness probe on a 3.6k-file repo: no-op index 0.19s.

• Nested plain repos (monorepo of independent .git checkouts, no
  .gitmodules): ls-files silently skips their subtrees — untracked dirs
  carrying a .git are enumerated recursively; any level that can't take
  the git path falls the whole enumeration back to the walker.
• .codegraphignore applied on the git listing (root-level, cascades
  into nested repos) — no more walker fallback just because the file exists.
  Submodules (.gitmodules) still force the walker: dropping submodule
  symbols would be a false negative.
• Walker parity: hidden(false) — dot-dirs carry real content
  (.claude/ agent docs, .github/), and git enumerates them; junk
  dot-dirs stay excluded via EXCLUDE_DIRS.
• Engine-version gate: the rebuild stamp now includes the release
  version alongside PARSER_VERSION — every upgraded binary rebuilds
  automatically; a resolver change nobody remembered to stamp can no longer
  serve a stale-engine graph.
• Cross-process index lock: MCP server, its watcher thread, and parallel
  CLI runs serialize on a PID-stamped lock file; dead owners are stolen
  instantly (kill -0 liveness + stale-age window), so a kill -9 mid-index
  never bricks the next query — verified live: the orphaned lock was stolen
  by the very next search, which self-healed and answered.
• Binary sniff: a NUL byte in the first 8KB (generated blobs with code
  extensions — valid UTF-8) keeps the file manifested but contributes zero
  symbols.
• Ambiguous-candidate ranking (MCP callers): strongest resolved evidence
  first, cross-language ties broken toward the language family the textual
  evidence lives in. Ranking only — never changes which edges exist.
• CODEGRAPH_MCP_CONCISE=1: drops per-response coaching fields
  (_hints, explainer notes); coverage/_fallback/truncation notes always
  stay. Measured 265→166 B on a callers answer.

Receipts: branch-switch storm (150 files) heals partially in 0.12s with
exactly reversible node counts; git-vs-walker parity proven on an identical
tree (1200 == 1200 nodes); verify-determinism byte-identical on a 3.6k-file
repo; zero phantom edges on 71k- and 25k-edge live graphs.