Add sessions() as first-class entry point for session discovery with
project/time/branch filters. Extend summaries, workflows, failures,
subagents, fileHistory with the same opts vocabulary that search()
already had — no more pulling full datasets to filter client-side.
Prepares for adding Codex JSONL support — new indexers can be added
without touching the query layer.
- db.mjs: schema, openDb, truncation helpers, shared utilities
- indexer.mjs: file discovery, JSONL parsing, SQLite writes
- query.mjs: all query API functions (search, context, raw, etc.)
- runtime.mjs: thin CLI entry point + VM script executor