Preserve Codewith titles parentage and provenance during ingestion

[andrei-hasna]

Problem

Generic rollout parsing loses Codewith-specific titles and root/subagent relationships and can fall back to an unsuitable first-message title.

Acceptance

• Enrich titles from session_index.jsonl.
• Preserve structured parent/subagent relationships.
• Preserve timestamps, model/provider, cwd/project path, machine, and source path.
• Never ingest or emit auth-profile or credential metadata.
• Round-trip fixtures cover root and subagent sessions.

Todo: OPE2-00080