Speed up initial full indexing

[Widthdom]

Summary

• reduce empty-database full-index time by optimizing SQLite batch parameters, authoritative fresh inserts, RETURNING row mapping, and deferred reference indexes
• avoid impossible or repeated symbol-regex work through required-literal gates and recoverable-miss caching
• materialize C# instantiation candidate families set-wise and reuse reference-line extraction state across C#, Java, Kotlin, and Swift paths
• add cold-path, persistence, graph parity, concurrency, cancellation, and allocation regression coverage

The repository-scale Release cold-index benchmark improved from 102.8 seconds on origin/main to 55.96 seconds at this head (45.6% faster), while indexing 1,423 files, 52,050 symbols, and 510,274 references. Total allocation was 17.35 GB, down from approximately 19 GB.

Validation

• dotnet restore CodeIndex.sln --locked-mode -m:1 -p:UseSharedCompilation=false
• dotnet build CodeIndex.sln --configuration Release --no-restore -m:1 -p:UseSharedCompilation=false — 0 warnings, 0 errors
• full Release tests:
  • net8.0: 11,816 passed, 0 failed, 9 skipped
  • net9.0: 11,336 passed, 0 failed, 426 skipped
• dotnet format whitespace CodeIndex.sln --verify-no-changes --no-restore --verbosity minimal
• dotnet run --project tools/CodeIndex.Changelog --configuration Release --no-build -- check — 11 fragments validated
• git diff --check origin/main..HEAD
• empty-database Release full index plus status --check — workspace matched, graph/fold ready, no reference-extraction cap hits
• canonical root and workspace status --check — all members ready
• independent adversarial review: No blocking/actionable issues found.

Documentation and changelog

Updated DEVELOPER_GUIDE.md and TESTING_GUIDE.md.

Changelog fragments:

• changelog.d/unreleased/+authoritative-fresh-raw-bulk-inserts.changed.md
• changelog.d/unreleased/+authoritative-fresh-reference-index-deferral.changed.md
• changelog.d/unreleased/+cold-full-index-contract.internal.md
• changelog.d/unreleased/+csharp-impossible-regex-probes.internal.md
• changelog.d/unreleased/+csharp-instantiation-fallback.changed.md
• changelog.d/unreleased/+csharp-recoverable-regex-cache.changed.md
• changelog.d/unreleased/+fresh-reference-integration-contracts.internal.md
• changelog.d/unreleased/+numeric-batch-parameters.changed.md
• changelog.d/unreleased/+reference-line-ordinals.changed.md
• changelog.d/unreleased/+reference-line-resolver-reuse.changed.md
• changelog.d/unreleased/+symbol-required-any-literals.changed.md

Follow-up candidates

None identified.