Add vitest coverage for router, pages, and tool renderers #162

Job	Run time
Frontend unit tests (vitest) (ubuntu-latest)	19s
pytest (ubuntu-latest)	43s
mypy	23s
pytest (macos-latest)	26s
Frontend unit tests (vitest) (windows-latest)	1m 4s
ruff + pip-audit (ubuntu-latest)	21s
ruff + pip-audit (macos-latest)	20s
Frontend unit tests (vitest) (macos-latest)	19s
API integration tests + coverage (windows-latest)	46s
Verify prod requirements.txt is sufficient	7s
ruff + pip-audit (windows-latest)	1m 10s
pytest (windows-latest)	1m 8s
API integration tests + coverage (ubuntu-latest)	17s
Performance benchmarks (informational)	25s
API integration tests + coverage (macos-latest)	16s
	8m 4s

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