fix(ci): stabilize Vercel deploy health checks, rollback automation, and SIS startup ping

[Copilot]

Summary

Stabilizes production deployment flow by hardening Vercel health verification and rollback behavior that was generating recurring deployment incidents. Also adds a non-blocking SIS memory ping during web startup for early memory-service reachability signaling.

Changes

• CI/CD concurrency + cancellation safety
  • Set deploy workflows to cancel-in-progress: false to avoid interrupting in-flight release/deploy mutations.
• Production deploy/health-check hardening
  • Capture and validate the actual Vercel deployment URL from the production deploy step.
  • Run retried health checks against that deployment URL (site + /api/health) with explicit timeouts.
  • Keep canonical-domain probe as informational, not a hard gate.
• Rollback automation improvements
  • Trigger rollback path when either production deploy or post-deploy health check fails.
  • Attempt automated vercel rollback <deployment-url> when URL is available.
  • Emit richer incident issue context (failed stage, deployment URL, job results).
• Web startup SIS memory ping
  • Added one-time, server-side, non-blocking startup ping helper with timeout and safe failure handling.
  • Wired into app startup path (layout.tsx).

# mvp-deploy.yml
concurrency:
  group: mvp-deploy-${{ github.ref }}
  cancel-in-progress: false

Type

• Feature (new functionality)
• Fix (bug fix)
• Refactor (code improvement, no behavior change)
• Docs (documentation only)
• Lore (universe content, Library texts)

Checklist

• TypeScript compiles with zero errors (pnpm build)
• Changes align with ARCANEA_CANON.md (if lore-related)
• No new any types introduced
• Tested locally or verified in Vercel preview

Original prompt

Implement immediate stabilization fixes: Update CI/CD to resolve Vercel health check deployment failures (issues #64-67), add better error handling and rollback automation. Integrate basic SIS memory ping in the web app startup. Make it production-ready within this PR.

[vercel]

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Project	Deployment	Actions	Updated (UTC)
arcanea-2	Error		Jun 16, 2026 9:29pm
arcanea-web	Ready	Preview, Comment, Open in v0	Jun 16, 2026 9:29pm

[vercel]

Deployment failed with the following error:

Invalid vercel.json file provided