Add vitest coverage for router, pages, and tool renderers #163

Job	Run time
Performance benchmarks (informational)	29s
API integration tests + coverage (ubuntu-latest)	21s
ruff + pip-audit (ubuntu-latest)	24s
pytest (windows-latest)	1m 32s
Verify prod requirements.txt is sufficient	8s
ruff + pip-audit (macos-latest)	19s
pytest (ubuntu-latest)	37s
ruff + pip-audit (windows-latest)	1m 12s
mypy	17s
Frontend unit tests (vitest) (ubuntu-latest)	23s
Frontend unit tests (vitest) (macos-latest)	20s
pytest (macos-latest)	37s
API integration tests + coverage (macos-latest)	14s
Frontend unit tests (vitest) (windows-latest)	48s
API integration tests + coverage (windows-latest)	49s
	8m 30s

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