docs: contributor onboarding path + CODEOWNERS for bus-factor mitigation #290

Job	Run time
mypy	19s
Frontend unit tests (vitest) (windows-latest)	1m 5s
Verify prod requirements.txt is sufficient	13s
ruff + pip-audit (windows-latest)	1m 2s
Frontend unit tests (vitest) (macos-latest)	39s
API integration tests + coverage (macos-latest)	24s
Frontend unit tests (vitest) (ubuntu-latest)	26s
API integration tests + coverage (ubuntu-latest)	20s
pytest (ubuntu-latest)	43s
Performance benchmarks (gated)	32s
ruff + pip-audit (macos-latest)	17s
pytest (windows-latest)	1m 24s
ruff + pip-audit (ubuntu-latest)	23s
pytest (macos-latest)	44s
API integration tests + coverage (windows-latest)	56s
	9m 27s

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