CI-001A — Repair the deterministic frontend test baseline

[daliu]

Problem

The frontend Jest environment lacked Web Encoding/Stream globals required by Firebase dependencies, and the only application test still asserted the obsolete Create React App starter page. This prevented the test suite from being a usable CI gate.

Outcome

Provide a deterministic no-network frontend baseline that runs the real app smoke route and supports Firebase imports without weakening production code.

Scope

• src/setupTests.js
• src/App.test.jsx
• Test-only mocks needed to prevent Firebase network access
• Excludes workflow gating, non-mutating lint migration, dependency upgrades, and deployment identity

Acceptance criteria

• Frontend tests execute under CI mode without TextEncoder/stream failures.
• The smoke test asserts the current MPRC home route and accessibility skip link.
• Tests make no Firebase/provider network calls.
• Existing focused Firebase/Sentry isolation tests continue to pass.
• Production compile and diff check pass.

Dependencies

None for the test harness. This child is the baseline prerequisite for the remaining CI-001 deployment work.

Coordination

A verified local working-tree implementation predates publication of this issue. This issue records the exact ownership boundary before any further editing or PR work. The existing diff must be isolated onto the claimed branch before review; unrelated changes and the pre-existing public/sitemap.xml modification are excluded.

Do not edit the listed paths or duplicate this outcome while the issue is assigned and has a valid timestamped CLAIMED marker.

[daliu]

CLAIMED by Codex agent /root at 2026-07-12T20:50:20Z; branch codex/issue-103-frontend-test-baseline.

Existing shared working-tree implementation predates issue publication. I will isolate this outcome onto the named branch serially before opening a PR; no unrelated dirty path is included.

[daliu]

Parent tracker: #105. This claim covers CI-001A only; deployment gating, lint migration, OIDC/IAM, and backend-first rollout remain unclaimed tracker children.