fix(cli): remove stale capture index rows

[zxy1553]

Summary

Fix stale rows in the captures SQLite table when capture JSON files are removed.

Changes:

• clean captures now deletes matching captures rows after removing capture-buffer/*.json
• rebuild-captures-index now removes rows whose capture files no longer exist
• adds regression tests for cleanup and rebuild behavior

Tests

• python -m pytest tests/test_cli_captures_cleanup.py -q
• python -m ruff check src/openchronicle/cli.py tests/test_cli_captures_cleanup.py

[gemini-code-assist]

Code Review

This pull request introduces synchronization between the capture buffer directory and the database index. It updates rebuild_captures_index to remove stale database entries and _clean_captures to delete records when files are unlinked. New tests have been added to verify these cleanup operations. The review feedback suggests wrapping database deletion loops in transactions to improve performance in SQLite.

[gemini-code-assist]

The loop performs multiple database deletions in autocommit mode, which is inefficient in SQLite. Wrapping the loop in a transaction (e.g., using with conn:) will improve performance by grouping these operations into a single commit.

Suggested change

	with fts.cursor() as conn:
	with fts.cursor() as conn, conn:

[gemini-code-assist]

The loop performs multiple database deletions in autocommit mode. Wrapping the loop in a transaction will improve performance.

Suggested change

	with fts.cursor() as conn:
	with fts.cursor() as conn, conn: