P3.1 TaskStore trait + SQLite backend (tables 1-7) - Verification complete

Verified that the TaskStore trait and SQLite backend implementation
for tables 1-7 is complete and all acceptance criteria are met.

All 15 tests pass:
- CRUD operations for all 7 tables
- Idempotent migrations with schema versioning
- Concurrent writes (WAL mode + 5s timeout)
- Persistence across DB re-opening
- Health check functionality

Non-obvious requirements verified:
- tasks.node_tasks is JSON via serde_json
- idempotency_cache.body_sha256 is BLOB (32 bytes)
- jobs.claim_expires_at supports heartbeat updates
- leader_lease uses row presence as advisory lock

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.beads/traces/miroir-r3j.1/metadata.json

@@ -5,11 +5,11 @@
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-  "captured_at": "2026-05-13T22:43:12.689737967Z",
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   "trace_format": "claude_json",
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.needle-predispatch-sha

@@ -1 +1 @@
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