refactor: shared session load path for session and export APIs #271

Job	Run time
pytest (windows-latest)	2m 26s
Performance benchmarks (gated)	39s
mypy	24s
API integration tests + coverage (windows-latest)	1m 17s
pytest (macos-latest)	30s
Frontend unit tests (vitest) (macos-latest)	47s
Frontend unit tests (vitest) (windows-latest)	1m 1s
Verify prod requirements.txt is sufficient	11s
ruff + pip-audit (macos-latest)	24s
pytest (ubuntu-latest)	41s
API integration tests + coverage (ubuntu-latest)	22s
ruff + pip-audit (ubuntu-latest)	30s
API integration tests + coverage (macos-latest)	20s
ruff + pip-audit (windows-latest)	1m 11s
Frontend unit tests (vitest) (ubuntu-latest)	28s
	11m 11s

Provide feedback