feat: org-wide alert on consecutive Vercel-deploy failures across refokus-agency

[taprile314]

Problem & Motivation

There is no alert today on repeated Vercel-deploy failures across refokus-agency. A recent postmortem showed a real failure stayed hidden for ~48h over the weekend because nothing surfaced it. Without a signal that fires when something is consistently broken, low-merge-activity windows mask incidents.

Adding the alert today would not work: transferred custom-code repos generate constant deploy failures and would drown the alert in false positives. That cleanup is tracked in #20 — this issue is blocked by it.

Scope

• Define the alert: threshold (e.g. N consecutive failed deploy runs in a single repo, or M failures across the org in a window), scope (which workflows / which repos), and delivery channel.
• Implement the alert against GitHub Actions runs (recommended via a scheduled workflow in platform querying the API, or via existing monitoring tooling if there is one).
• Verify end-to-end with an intentional failure or replay.

Acceptance Criteria

• Alert threshold is explicit and documented (in this issue or linked).
• Alert is delivered to a channel the team actually watches (Slack channel TBD).
• Alert verified end-to-end (intentional failed deploy or replay) before closing.
• After the transferred-repo flag ships (feat: add transferred-repo flag in deploy.yml to skip Vercel deploys cleanly #20), zero false positives from umh-custom-code / profile-behavior-custom-code.

Risks & Constraints

• Threshold tuning is a judgment call — start conservative (e.g. 3 consecutive failures in the same repo) and iterate based on observed signal/noise.
• Hard-blocked by feat: add transferred-repo flag in deploy.yml to skip Vercel deploys cleanly #20: shipping this before the flag means constant false positives from transferred repos and the alert gets muted.

Edge Cases

• Dependabot deploy runs are already skipped (if: github.actor != 'dependabot[bot]') and should not count as failures.
• Manual workflow_dispatch runs intentionally failed during testing — decide whether to exclude or accept as noise.

Blocked by #20.