Keep inherited batch database provenance consistent in status output

[Widthdom]

Summary

When batch --db <path> supplies the database for a child status command, the child reads counts and index metadata from that database but builds response metadata and Git freshness against the current working directory's canonical repository/database.

One response therefore mixes two repositories and can report a false head_changed: true.

Reproduction

Verified on origin/main at 8d537125aae747c1008ad31b3d59364cb43652f0 with cdidx 1.42.0.

Create or reuse a database for a different scratch project, then run from the CodeIndex repository:

{"command":"status","args":["--json","--compact"]}
{"command":"search","args":["anything","--json","--limit","1"]}

dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll batch \
  --db /tmp/cdidx-batch-repro/.cdidx/codeindex.db \
  --json-summary < /tmp/cdidx-batch-repro/commands.ndjson

Observed in the child status response:

• file/symbol counts and indexed_head came from the scratch database;
• metadata.db_path pointed at the canonical CodeIndex worktree database;
• runtime Git HEAD/freshness came from the CodeIndex worktree;
• head_changed was consequently true even though a direct status --db /tmp/.../codeindex.db was consistent.

Expected behavior

A database inherited from the batch parent must be treated exactly like a child-explicit --db for:

• data reads;
• reported database path;
• project-root resolution;
• indexed/runtime Git provenance;
• freshness and readiness decisions;
• all JSON metadata and diagnostics.

No field in one child response should silently describe a different repository.

Implementation guidance

• Propagate a single resolved database/project context into child dispatch, not only a thread-static reader.
• Prefer injecting the inherited --db into the child options or passing a typed resolved context through query execution.
• Do not re-resolve canonical DB/project metadata from CWD once a parent-pinned DB is active.
• Ensure nested/batched execution cannot leak context between child records, including exceptions and cancellation.
• Keep child-explicit --db precedence and mismatch validation deterministic.

Likely implementation areas:

• src/CodeIndex/Cli/BatchExecution.cs
• src/CodeIndex/Cli/QueryCommandRunner.Database.cs
• src/CodeIndex/Cli/QueryCommandRunner.Status.cs
• batch dispatch in src/CodeIndex/Cli/QueryCommandRunner.Batch.cs

Required tests

Use two repositories/databases with deliberately different paths, file counts, indexed commits, and runtime HEADs.

Cover:

1. parent-only --db;
2. child-explicit --db;
3. any permitted parent/child override or mismatch case;
4. multiple children to prove no context leakage;
5. text, regular JSON, compact JSON, and JSON summary provenance.

Assert every provenance/freshness field belongs to the same selected database. Add English and Japanese changelog fragments.

Regression history

This is a follow-up to #4354, which fixed mixed database behavior when a child supplied an explicit --db. The uncovered case is parent inheritance. It is also related to the CWD Git-provenance leak addressed in #152. Both are closed; no open exact duplicate was found.

[Widthdom]

Work started on branch fix-issue5083. I will keep the batch-inherited database context consistent across child status dispatch and add regression coverage for provenance, freshness, output modes, and context isolation.