Fix 43 test failures across 11 test files

[itsmiso-ai]

Parent umbrella issue: #616
Source audit: Weekly tech debt audit: dispatch - 2026-07-15
Source audit date: 2026-07-15

Recommendation

Problem: 43 tests fail in vitest run but do not break CI. Four unit test files are missing @vitest-environment node directives and fail with "No such built-in module: node:" errors. Seven component tests fail under jsdom due to rendering/styling/environment mismatches. This creates a false sense of test health — CI does not catch regressions in these files.

Evidence:

• npx vitest run outputs: "Test Files 11 failed | 103 passed | Tests 43 failed | 1870 passed"
• Missing directive files: src/lib/github.test.ts, src/lib/version.test.ts, Dockerfile.test.ts, src/app/api/pr-followup/webhook/route.test.ts
• Failing component files: layout.test.tsx, auth-controls.test.tsx, github-link.test.tsx, issue-card.test.tsx, kanban-board.test.tsx, kanban-column.test.tsx, login/page.test.tsx

Acceptance: All 1913+ tests pass in npx vitest run. CI includes the full test suite in its success/failure check.