Split the artifact and Stage 12 cache precompute modules

precompute.py (931 lines), stage12_cache/precompute.py (844 lines) and
tests/test_precompute.py (1,835 lines) were over the file-length limits.
The code moves unchanged.

Each precompute module keeps its manifest functions, its functions
dataclass and run_precompute, and re-exports every public name in
__all__, so the Modal precompute apps, which import the step functions
from it when they run, are unchanged. The steps move to three modules
next to it:

- precompute_planning.py: cohorts or baseline identities, the state
  dataset targets, plan_artifacts_impl and select_work
- precompute_datasets.py: the national and per-state dataset builds
- precompute_baselines.py: computing the baselines and checking that
  they are deterministic

Private names another module now uses are public: the artifact
precompute's _cohort_resolution, and the cache precompute's
_scoped_planned_simulation (with a new docstring) and _baseline_identity.
stage12_worker_validation.py imports scoped_planned_simulation from the
cache's precompute_planning.py.

tests/test_precompute.py keeps the schema, planning and orchestration
tests; the rest move to test_precompute_planning.py,
test_precompute_datasets.py and test_precompute_baselines.py, all 71
tests unchanged apart from patch targets. Each patch now targets the
module whose code reads the name: the planning tests patch
state_dataset_targets and cohort_identity in precompute_planning, the
state dataset tests patch state_dataset_targets in precompute_datasets,
and the determinism tests patch _prepare_cohort_baseline in
precompute_baselines. In the cache tests, the planning fixture and the
state-target test patch precompute_planning, the state build fixture
patches precompute_datasets, the determinism tests patch
precompute_baselines, and the store helper replaces Stage12CacheStore
in all four modules, each of which opens the store.

The file-length baseline drops the three files (count 7 to 4).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: anth-volk

changelog_entry.yaml

@@ -16,6 +16,7 @@
       - Ran Stage 12 US national simulations as 20 region-group calls each, and built an independent, immutable Stage 12 cache of three annual US datasets and 60 current-law baselines before each deployment, publishing it only after a recorded determinism check and recording its release in the v2 version manifest under a new key, while the existing key keeps a copy that earlier readers accept
       - Made the budget refuse a household count outside its country's plausible range (above 200 million in the US or 60 million in the UK, negative or not finite), raising ImplausibleEntityCountError instead of publishing a count like #767's
     changed:
+      - Split the artifact precompute (precompute.py, 931 lines) and the Stage 12 cache precompute (stage12_cache/precompute.py, 844 lines) each into planning, dataset-building and baseline modules, with the manifest and run_precompute left in the original module, which re-exports every public name, so the Modal precompute apps and their tests import from the same paths; the cache precompute's _scoped_planned_simulation and _baseline_identity are now public, and the worker validation imports scoped_planned_simulation from its new module; the 1,835-line precompute test file is split into four, and the cache precompute tests patch each name in the module whose code reads it
       - Split the 4,709-line Stage 12 runtime test file into thirteen test files by behaviour (dataset loading, provenance, the single worker and its failures, aggregates, the coordinator and its failures, runtime store retries, failure records, cancellation, child state errors and the wait window) and three support modules for the shared builders, fake stores and fake child calls, whose helpers are now public; the other Stage 12 tests import them from those modules, every test keeps its name and body, and two parametrized cases are named after the renamed bundle helper
       - Split Stage 12 report coordination (stage12_runtime/coordination.py, 1,091 lines) into modules for the report coordinator class, its child simulations' records, failures and cancellation, and the parent report's checks and claim, with coordinate_report and every public name still in coordination.py and child failures still logged under its logger; and turned the contract's stage12_execution.py (929 lines) into a stage12_execution package of modules for the shared field types and simulation input, report inputs and output plans, result artifacts, and comparison-run records, which re-exports every name from the same import path, with unchanged JSON schemas; models subclass the base models through the package path ruff.toml lists, so no ruff setting changes
       - Split the gateway's endpoints.py (1,454 lines) into modules for the shared router and request helpers, route resolution from the active routing state, Modal reads of job metadata and routing, bundle payloads, and the job submission, job status and version routes, which register their routes in the same order, so the OpenAPI document is unchanged; endpoints.py re-exports every public name, the routes keep logging under the policyengine_simulation_gateway.endpoints logger, and the private helpers the new modules share are now public; its 1,801-line test file is split into five test files, with the shared expected-response helpers in fixtures/gateway_responses.py

docs/generated/rules.md

@@ -66,7 +66,7 @@ Every rule that governs `policyengine-sim-api` is listed here with how it is enf
 
 - `sim.ci.multiline-run-is-script`: 13 remaining in `rules/baselines/ci-multiline-run.txt`
 - `sim.microdata.weight-stripping-confined`: 0 remaining in `rules/baselines/sim-microdata-weight-stripping.txt`
-- `sim.quality.python-file-length`: 7 remaining in `rules/baselines/python-file-length.txt`
+- `sim.quality.python-file-length`: 4 remaining in `rules/baselines/python-file-length.txt`
 
 ### Exceptions and review dates