Surface data email send failures as ERROR instead of silent drop

[cipher813]

Summary

Fix a silent-fail in `weekly_collector._finalize` where a failed `send_step_email` would log WARNING and continue, giving the run no visible indication that monitoring was blind to it.

Context

`_finalize`'s email block:
```python
if not dry_run and only is None:
try:
from emailer import send_step_email
step_name = f"Data Phase {phase}" if phase else "Data Collection"
send_step_email(step_name, results, run_date)
except Exception as exc:
logger.warning("Step email failed (non-fatal): %s", exc)
```

Two problems:

1. Dead try/except — `send_step_email` is explicitly documented as "Never raises" (see `emailer.py:20`) and returns `True`/`False`. No exception ever propagates out of it.
2. Discarded return value — when both Gmail SMTP and SES fallback failed inside `send_step_email`, the function returned `False`. The caller ignored it.

Net effect: a successful data collection with a broken emailer recorded in S3 correctly but emitted no notification. Monitoring couldn't distinguish "ran and emailed" from "ran and silently dropped the notification".

Fix

• Remove the dead `try/except`
• Check the boolean return value
• On `False`, log ERROR with enough context to diagnose (which env vars / SES identity to check)

Not raising on email-send failure because the data itself is valid in S3 and downstream Step Function steps still consume it — email is a monitoring layer, not a data dependency. If CloudWatch alarms are wired to ERROR-level log events on this Lambda, the missed email surfaces naturally.

Audit of other silent-fail patterns in weekly_collector.py

• Lines 130, 363, 369 — S3→Wikipedia fallback for constituents. Intentional. Downstream `if not tickers: return failed` catches the empty case.
• Lines 443, 483 — duration formatting `try/except: pass`. Cosmetic. Acceptable.
• run_daily status logic (lines 428-432) — only produces `ok` or `failed`, no `partial`. `main()` hard-fails on anything != `ok`. Already correct.

No other silent-fails found in this file worth addressing.

Test plan

• 61 existing tests pass locally
• CI green
• If a future emailer misconfiguration occurs, the next Saturday DataPhase1 run logs `Step email '...' failed to send` at ERROR level

🤖 Generated with Claude Code