- cloud/attempt_ledger.py: separate task_attempts table (not tasks
columns) with per-attempt rows, MAX+1 attempt_no, append-only
intent; interrupted rows kept but never counted; is_defect is
explicit, never inferred from failure; first defect category
wins; no-ledger tasks stay unknown (None), never backfilled.
SQLite DDL is CREATE TABLE IF NOT EXISTS (idempotent); PG_DDL
is the verbatim manual step for production Postgres, kept out
of POSTGRES_SCHEMA on purpose (migrations coverage untouched).
- cloud/server.py GET /metrics-report: aggregates the ledger
into compute_metrics records; missing ledger table degrades to
unknown rates, not an error. Cost dual-column code untouched.
- cloud/metrics.py: docstring only (ledger is now the source);
compute_metrics logic and all #238 semantics unchanged.
- Tests: 16 ledger tests (store/aggregate/metrics/PG adapter
evidence) + 3 endpoint tests (real rates, old task beside
ledger task, interrupted status non-terminal).
