feat: track E2E coverage by required scenarios, not only routes

[aasimsyed]

Terms

• I have searched open and closed feature requests
• I agree to follow activist's Code of Conduct

Description

#1959 counts a route as covered if a spec opens the URL. That does not mean the behaviors on the page are tested.

Add a required-scenario catalog and a script that scores it against current specs. Route hits stay as a secondary check.

Related: #1972 (do not close). Detect stub pages from :underDevelopment / empty templates instead of a hardcoded list.

Task

• Add frontend/test-e2e/scenario-matrix.mjs (flows, cases, ID_PREFIXES, CATEGORIES)
• Score it in e2e-coverage.mjs: --full, --out (gitignored test-results/e2e-coverage-latest.md), --json
• Add yarn test:e2e:coverage
• Document how to run the report and add a catalog row in FRONTEND_TESTING.md

Ids are PREFIX-CATEGORY-NN (example: EF-PERM-01 = event FAQ, permissions, first case). covered = spec path matches, and test() title matches when required. partial = only skip / fixme. missing = no match.

Acceptance criteria

• --full --markdown --out reports covered / partial / missing per flow, with readable id legends
• A new c(...) row shows up on the next run
• Route % is still reported and labeled secondary
• Remove stub route detection from e2e-coverage.mjs #1972 stays open

Contribution

I'll implement this.