Client-owned conversation transcript projections for Hooks v2.
Materializes versioned per-thread and per-subagent JSONL files that hook
commands can read via transcript_path / agent_transcript_path.
Lag semantics:
The on-disk JSONL may lag behind live checkpoint/UI state. Callers that need
the just-finished assistant turn must prefer last_assistant_message on
Stop/SubagentStop. materialize() flushes pending records immediately before
returning a path so hooks see a consistent snapshot of what the store has
accepted so far, not a live tail of the server checkpoint.
Redact secret-like strings inside transcript content.
One JSONL record in a materialized transcript projection.
Identity of a materialized transcript file.
Append-only JSONL transcript projections owned by the client process.
Collect completed stream messages into a Hooks transcript runtime.
