fix: fail CI on test timeout and upload vitest report on failure (closes #706)

[boalambo]

Problem

The test step in .github/workflows/ci.yml wrapped vitest run in a
shell timeout with || exit 0. This caused the CI job to always exit
with code 0 — even when tests failed or the suite timed out — giving
false confidence and allowing broken builds to be merged undetected.

Changes

• Removed the || exit 0 fallback and the shell timeout wrapper
• Added timeout-minutes: 5 directly on the Run Tests step so
  GitHub Actions enforces the limit and fails the job on expiry
• Added --reporter=json --outputFile=vitest-report.json to Vitest
  so a structured report is written during the run
• Added an Upload test report on failure step that uploads
  vitest-report.json as a CI artifact when the job fails

Acceptance Criteria

• A test suite timeout causes the CI job to exit with a non-zero code
• The pipeline blocks the PR merge when tests timeout
• Test output is available as a CI artifact for debugging

Impacted Files

• .github/workflows/ci.yml

Closes #706

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[boalambo]

The 14 type errors flagged by the type-check job are pre-existing and
unrelated to this PR. They originate from files being actively worked
on in PR #836 (issue #753), which is replacing console.* calls with
the structured logger. Fixing them here would conflict with that PR.
These will be resolved once #836 is merged.