docs: contributor onboarding path and CODEOWNERS #299

Job	Run time
Verify prod requirements.txt is sufficient	7s
pytest (macos-latest)	34s
API integration tests + coverage (windows-latest)	1m 18s
pytest (ubuntu-latest)	53s
ruff + pip-audit (macos-latest)	22s
API integration tests + coverage (macos-latest)	18s
mypy	32s
Frontend unit tests (vitest) (macos-latest)	26s
Frontend unit tests (vitest) (ubuntu-latest)	31s
ruff + pip-audit (windows-latest)	1m 7s
ruff + pip-audit (ubuntu-latest)	19s
API integration tests + coverage (ubuntu-latest)	17s
Performance benchmarks (gated)	29s
Frontend unit tests (vitest) (windows-latest)	1m 35s
pytest (windows-latest)	1m 21s
	10m 9s

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