Harden test determinism and restore frontend CI gating

[rendall]

Summary

Implements Phase 03: test determinism and CI hardening.

This PR completes checklist items C01-C11 and restores required frontend test gating in CI while preserving full locale coverage.

What changed

Backend test env determinism

• Added backend Jest setup env injection:
  • src/tests/backend/setup-env.ts
  • wired via setupFiles in jest.backend.config.ts
• Backend tests now derive missing env values from example.env and inject deterministic non-default values for *SECRET*/*PASSWORD*.
• Refactored src/tests/backend/secrets.test.ts:
  • removed hard failure on .env file existence
  • kept local onboarding signal as non-blocking warning

Frontend locale/date determinism (full matrix preserved)

• Refactored src/tests/frontend/frontend-utilities.test.ts:
  • replaced brittle exact-locale prose assertions with deterministic structural checks
  • kept the full existing locale matrix
  • added locale support/resolution guardrails
  • normalized fixtures to UTC-stable inputs
  • retained integration-style localized rendering check
• Updated test script wiring to run frontend tests with TZ=UTC:
  • package.json
  • yarn.lock (added cross-env)

CI hardening and gating

• Updated .github/workflows/netlify-api-test.yml:
  • removed .env bootstrap command (node ./scripts/createTestEnv.mjs) from backend test path
  • set TZ=UTC for test execution
  • restored frontend CI gating by running yarn test:frontend in required workflow
  • kept existing MongoDB binary pinning behavior intact

Documentation

• Added and completed Phase 03 checklist:
  • docs/plans/phase-03-checklist.md
• Hardened plan with QC/integration/sanity pass decisions:
  • docs/plans/phase-03-test-determinism-and-ci-hardening.md
• Added implementation convention final clean pass:
  • docs/norms/implementation.md (yarn run fix before PR)
• Updated README test section with deterministic test contract:
  • backend tests do not require .env on disk
  • frontend tests run under TZ=UTC

Validation

• yarn test:backend (with .env present)
• yarn test:backend (with .env temporarily removed)
• yarn test:frontend
• yarn test
• yarn run fix then yarn test again

All suites pass locally after changes.

Scope notes

• No locale removals; i18n coverage remains full-matrix.
• No product formatting redesign; only test determinism and CI gating hardening.

[Copilot]

Pull request overview

This PR hardens test determinism across backend and frontend suites and restores required frontend test gating in CI, while preserving the existing full locale coverage.

Changes:

• Inject backend test environment variables deterministically from example.env via a Jest setupFiles hook (including non-default secret/password values).
• Refactor frontend longFormatDate tests to avoid brittle exact-string assertions while keeping the full locale matrix, and run frontend tests under TZ=UTC.
• Update CI workflow to remove .env bootstrapping, set TZ=UTC, and run both backend and frontend test suites as part of the required gate.

Reviewed changes

Copilot reviewed 10 out of 14 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
yarn.lock	Adds cross-env lock entry for cross-platform TZ=UTC script support.
package.json	Runs frontend tests with TZ=UTC via cross-env; adds cross-env to devDependencies.
jest.backend.config.ts	Wires new backend Jest setup file into setupFiles while preserving preset setup files.
src/tests/backend/setup-env.ts	New Jest setup file to load/inject env from example.env with deterministic secret/password values.
src/tests/backend/secrets.test.ts	Removes hard failure on missing .env; replaces with non-blocking onboarding warning.
src/tests/frontend/frontend-utilities.test.ts	Replaces brittle locale prose assertions with deterministic Intl-based structural/equality checks across full locale matrix.
.github/workflows/netlify-api-test.yml	Removes .env bootstrap, sets TZ=UTC, and restores frontend test gating alongside backend tests.
README.md	Updates test instructions to reflect deterministic backend env injection and frontend TZ=UTC contract.
docs/plans/phase-03-test-determinism-and-ci-hardening.md	Expands Phase 03 plan with explicit scope decisions and determinism strategy.
docs/plans/phase-03-checklist.md	Adds completed Phase 03 checklist mapping to implemented work items.
docs/norms/implementation.md	Adds “run yarn run fix before opening a PR” convention.
docs/archive/phase-02-backend-correctness-and-cors.md	Archives Phase 02 checklist documentation.
docs/archive/phase-01-5-ci-stabilization-and-test-gating.md	Archives Phase 01.5 CI stabilization/test gating documentation.
docs/archive/phase-01-5-checklist.md	Archives Phase 01.5 checklist documentation.

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