fix: harden raw storage and split storage modules

[davidrobertson]

Summary

• harden raw-log locking, durability, and failure reporting across hook and command paths
• split the storage facade into focused modules while preserving its public API
• update retrieval guidance, package docs, smoke coverage, and contract tests

Why

The review found cases where concurrent writers and failed lock publication could strand or lose access to durable raw events. This change keeps events.jsonl authoritative, makes lock recovery explicit, and separates derived storage work from the raw append path.

Impact

Capture and recovery are safer under concurrent or failed writes. The public storage surface stays intact, while the smaller modules make each storage responsibility easier to test and review.

Validation

• npm run typecheck
• npm test
• npm run smoke
• npm pack --dry-run --cache /tmp/codex-lcm-npm-cache