docs: contributor onboarding path and CODEOWNERS #300

Job	Run time
pytest (ubuntu-latest)	1m 1s
Verify prod requirements.txt is sufficient	7s
Performance benchmarks (gated)	34s
mypy	24s
pytest (macos-latest)	56s
API integration tests + coverage (macos-latest)	15s
Frontend unit tests (vitest) (windows-latest)	57s
Frontend unit tests (vitest) (macos-latest)	25s
API integration tests + coverage (windows-latest)	58s
ruff + pip-audit (windows-latest)	1m 3s
ruff + pip-audit (macos-latest)	31s
ruff + pip-audit (ubuntu-latest)	22s
API integration tests + coverage (ubuntu-latest)	17s
Frontend unit tests (vitest) (ubuntu-latest)	31s
pytest (windows-latest)	1m 46s
	10m 7s

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