refactor(models): narrow Any-typed parse boundary with TypedDict unions #139

Job	Run time
ruff + pip-audit (windows-latest)	1m 26s
API integration tests + coverage (ubuntu-latest)	23s
API integration tests + coverage (windows-latest)	1m 3s
pytest (ubuntu-latest)	24s
ruff + pip-audit (ubuntu-latest)	23s
mypy	22s
Verify prod requirements.txt is sufficient	10s
pytest (windows-latest)	1m 15s
Frontend unit tests (vitest) (windows-latest)	56s
Frontend unit tests (vitest) (ubuntu-latest)	20s
	6m 42s

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