fix(daily_closes): coalesce-arc hardening — polygon-transient / FRED-backoff / weekday-pull / restatement-severity (L4482/L4480/L4483/L4486)

[cipher813]

What

Four follow-ups to the 2026-06-01 FRED-429 / polygon-timeout incident. #354 made the system resilient to a missed value; these close the surrounding gaps the incident exposed. All in collectors/daily_closes.py + the weekday Step Function.

L4482 (P1) — macro backstop survives a transient polygon-fetch exception

collect() Step 1 now catches the transient network class (requests.Timeout / ConnectionError / PolygonRateLimitError) in polygon_only mode, logs loudly, and falls through to FRED (Step 2) + the macro yfinance backstop (Step 3). This is the exact gap that failed recovery re-run #1 — a polygon read-timeout aborted collect() before the FRED-index macro keys (^TNX/^VIX/^IRX/^VIX3M, which never come from polygon) could fill.
Narrow by design: PolygonForbiddenError (403) and the deliberate "0 tickers" empty-data RuntimeError still propagate with their own clear messages; a real equity outage still hard-fails at the coverage gate (0 equity records → <95%), so the catch cannot mask equity data loss.

L4480 (P1) — FRED backoff + jitter

New _fred_get_with_retry: bounded exponential backoff + full jitter on the transient class (429 / 5xx / timeout / connection), honors a server Retry-After when present, raises immediately on a deterministic 4xx (no point retrying a bad series_id). Stops the 429 storm at the source rather than only tolerating a missed value. Mirrors the in-repo polygon_client retry idiom; no new dependency.

L4483 (P2) — weekday SF MorningEnrich now git-pulls

infrastructure/step_function_daily.json MorningEnrich adds the same git -C … pull --ff-only origin main for alpha-engine-data + alpha-engine-config that the Saturday SF already runs. A same-day recovery re-run on a still-running instance no longer executes stale code (this incident cost a manual SSM git pull to deploy #354).

L4486 (P2) — discrepancy ERROR severity scoped

_log_close_discrepancies now emits FRED-index restatements toward the authoritative value at WARN (fred_restatement, excluded from the flow-doctor ERROR filter) while keeping ERROR for genuine cross-source equity drift. The reconciliation predictably restates VIX/TNX >5% when healing a 429-clobbered cell (5/14 VIX) or a stale T-1 edge cell (6/2) — desirable self-heals, not anomalies. Recording surface stays (per feedback_no_silent_fails) at the right level. Pattern observed twice (5/12, 6/2).

Tests

• New tests/test_daily_closes_coalesce_hardening.py (8): retry class (429→success, persistent-429 raises, 4xx not retried, timeout reraised), transient-non-fatal control flow + 403-still-propagates, restatement-vs-equity severity.
• Fixed two affected fixtures to set status_code (the helper now inspects it before raise_for_status).
• Full suite: 1785 passed, 1 skipped.

Deploy note

L4483 changes the weekday Step Function — needs the SF definition re-applied (CFN/Terraform/aws stepfunctions update-state-machine) for the git-pull to take effect; the daily_closes code changes deploy via the new MorningEnrich pull (or boot-pull). No S3 schema/path changes.

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