Stabilize SQLite policy audits and maintenance JSON

[Widthdom]

Summary

• Add info-level positive-evidence queries to sqlite-query-policy-surfaces for shared command creation, typed parameter helpers, identifier quoting, and PRAGMA helper usage.
• Return a structured E008_DB_ERROR JSON envelope for early corrupt SQLite DB failures in status --json while preserving existing stderr behavior after a DB is query-ready.
• Add wal_checkpoint_timing_note to real vacuum --json output and document the WAL checkpoint timing caveat in the English and Japanese developer guide sections.

Validation

• dotnet build CodeIndex.sln -p:UseSharedCompilation=false
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter "FullyQualifiedName~RunSearch_ListRecipesJsonIncludesBuiltInAuditMetadata_Issue3144|FullyQualifiedName~RunSearch_BuiltInRecipeSnapshotCoversNamesScopesAndQueries_Issue3692" -p:UseSharedCompilation=false
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter "FullyQualifiedName~RunDefinition_CountOnlyOnReadOnlyDbMissingChunks_FailsLikeDefinition|FullyQualifiedName~RunStatus_CorruptDbJsonReturnsStructuredError_Issue4338|FullyQualifiedName~RunVacuum_JsonExplainsWalCheckpointTiming_Issue4338|FullyQualifiedName~WithDb_OpenFailureBranchesSanitizeExceptionMessages_Issue4124" -p:UseSharedCompilation=false
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj -f net8.0 -p:UseSharedCompilation=false
• Combined net8/net9 full test run completed with net9 passing; net8 hit a transient ReleaseWorkflow_DockerEntrypointDropsRootToRequestedUidGid timeout, and the net8-only rerun above passed.
• dotnet run --project tools/CodeIndex.Changelog -- check
• dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll status --check --json
• dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll search --recipe sqlite-query-policy-surfaces --format count --summary-only --json --limit 5

Documentation And Changelog

• Updated DEVELOPER_GUIDE.md in both English and Japanese sections for the vacuum --json WAL timing note.
• Added changelog.d/unreleased/4302.fixed.md.
• Added changelog.d/unreleased/4338.fixed.md.

Review

• Ran adversarial review locally after implementation; the only issue found was over-broad JSON formatting for post-open query DB errors, which was narrowed and covered by the existing regression test.

Follow-Ups

• None.

Fixes #4302
Fixes #4338