New table sync_phase_failures(run_id, phase, error_summary, created_at)
with index on (phase, created_at). Minimal schema — no raw payload, no
PII — stores just enough to answer "did phase X fail in the last N
runs?" for the escalation check and the /api/sync/health pill.
Helpers in sqlite_service:
record_phase_failure(run_id, phase, error_summary)
INSERT OR REPLACE semantics (one row per run+phase), then prunes
to the most recent 100 sync_runs. error_summary clipped at 500
chars defensively.
get_recent_phase_failures(limit=3) → {phase: count} across the last N
runs, ordered by started_at desc.
6 unit tests cover creation, counting, pruning, empty state,
idempotency, and limit semantics.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
