v2: Add a consistent incremental Messages archive and search

[jmcte]

Problem / intent

Messages commands query the live chat.db directly. They have no DB/WAL-consistent snapshot, incremental cursor, local archive, watcher state, or full-text search. OpenClaw's imsgcrawl and imsg already define useful bounded JSON and action surfaces, so this repo should integrate deliberately instead of copying private IMCore behavior.

Acceptance criteria

• Document and implement the chosen adapter: internal archive or delegated imsgcrawl/imsg JSON integration.
• Read from a consistent snapshot via v2: Snapshot live SQLite stores consistently before querying #90 and never modify Apple's Messages database.
• Persist bounded incremental state, source fingerprint, freshness, conversation/message ids, and deletion behavior.
• Keep safe status/count output separate from sensitive bodies; bodies require explicit opt-in and retention policy.
• Add bounded conversation/message search with versioned machine output.
• Keep send/react/action capabilities outside the crawler provider and never require SIP disablement or dylib injection.
• Add synthetic DB/WAL, cursor, deduplication, group-chat, and redaction tests.

Dependencies

• Depends on v2: Define a versioned provider capability manifest #89, v2: Snapshot live SQLite stores consistently before querying #90, and the resumable archive issue.
• v2 follow-up to closed issue Add iMessage / Messages conversation inventory command #26.