[anth-volk]

Fixes #945

Same-Repository Draft PR Check

• This PR is a draft.
• This PR is from a branch in PolicyEngine/policyengine-sim-api, not a personal fork.

Summary

Eighth of nine stacked PRs; it builds on #942. It splits the entrypoint's app.py and its deployment asset tests without changing behaviour, and removes the last two files from the file-length baseline (count 2 to 0). Scripts compared every top-level statement of each old file with the new files: all appear exactly once and unchanged apart from the renames below and one logger line, in their original order, and every # noqa comment is kept.

src/policyengine_simulation_entry/app.py (925 lines)

Module	Lines	Holds
entry_runtime.py	400	the response constants, ComparisonBackend, the backend call and telemetry helpers, and EntryRuntime, which calls the backends and dispatches comparisons
app.py	583	the request-context middleware, every route, create_app, app, and re-exports of the moved public names

• Why the routes stay in app.py (583 lines, above the 400 the split aims for): their request annotations (SimulationRequest, UUID, AuthorizationDependency) come from imports that app.py also uses at runtime. Ruff doesn't recognise the routes' @app.post decorators, because app is a function parameter, so in a module of their own it reads those imports as typing-only and asks to move them under TYPE_CHECKING, which would stop FastAPI resolving the annotations. Keeping the routes in app.py keeps both behaviours as they are, with no suppression or settings change.
• Logging: entry_runtime.py names the policyengine_simulation_entry.app logger explicitly, so its records keep the logger name the tests check; this is the one statement that isn't verbatim. It is a logging.getLogger call in each module, not an import, so ruff still recognises the logger and the TRY400 suppressions on its calls stay in force.
• policyengine_simulation_entry.app:app, which the Dockerfile runs, and create_app are unchanged, and the entrypoint's OpenAPI tests pass unchanged.

Renames

Private names app.py now imports from entry_runtime.py are public: _EntryRuntime to EntryRuntime, _BackendCall to BackendCall, _model_json to model_json, _request_identifiers to request_identifiers, _route_template to route_template (the last three with a new one-line docstring), and _set_observability_header to set_observability_header.

Tests: tests/test_deployment_assets.py (2,251 lines)

File	Lines
test_deployment_assets_support.py (shared paths, shell and smoke fakes, GitHub expression reader; no tests)	411
test_deployment_assets.py	269
test_deployment_assets_cloud_run.py	280
test_deployment_assets_promotion.py	269
test_deployment_assets_release_gates.py	302
test_deployment_assets_routing.py	384
test_deployment_assets_traffic.py	197
test_deployment_assets_identity_smoke.py	303

• 126 tests before and after, with the same names. The shared helpers are public: _run_bash, _write_fake_smoke_curl, _smoke_test_env, _job_section, _sentinel_check_step, _routing_context, _run_identity_smoke and _workflow_jobs drop their underscore, and _gh_eval is evaluate_github_expression.
• The support module's name matches test_*.py, so the CI-script guard (sim.ci.workflow-scripts-tested), which looks for each workflow script's name in test files, still finds the scripts named by its path constants.
• Rules registry: every one of these tests was referenced by a rule's pytest nodes or listed in discovery.ignore_tests. rules/registry.toml now names each by its new file (63 references), and the guard-test discovery pattern is tests/test_deployment_assets*.py, so every test in the new files must still be registered or ignored. No rule, status or scope changes otherwise.
• Patch targets: test_comparison_dispatch_timeout_cannot_change_production_response patches STAGE12_MODAL_SUBMISSION_TIMEOUT_SECONDS in entry_runtime, where EntryRuntime reads it for the comparison dispatch; test_temporary_stage12_submission_has_a_hard_acknowledgement_timeout still patches it in app, where the Stage 12 submission route reads it; Stage12ComparisonBackend is still patched in app, where create_app reads it.

Environment variables

No change: the moved code reads no environment variable, and no workflow, image or deployment file changes.

Testing

• Entrypoint, full suite: 742 passed.
• Pyright for the entrypoint: no errors.
• Ruff 0.15.22 format and lint: clean.
• python -m unittest discover -s scripts/rules/tests -t .: passed.
• python scripts/run_quality_guards.py and python -m scripts.rules guard --base-ref origin/file-length-split-simulation-runtime: passed; python -m scripts.rules render leaves no diff.

Only the lowest PR in the stack runs full CI, so this PR's CI complete check fails by design until the PRs below it merge.

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