Task: Generate the compute and synthetic shell units

The two largest hand-written units are not one entity each. compute_commands.cpp is 1192 lines and synthetic_commands.cpp is 1094, and between them they cover apps, app versions, batches, workunits, hosts, concurrency policies, generation configurations, folders, templates and process parameters. Decide whether the facet can express them as generated units per entity; where it cannot, state what the model would have to carry and raise that as its own task. The outcome is generated units or a written reason, never two large files left unexplained.

• Every entity reachable in the two units is generated, or has a written reason and a task saying what the model must gain.
• The two hand-written files are deleted or reduced to the part that is genuinely not per-entity.
• Regenerating produces a no-op.

(Implementation strategy. Written when work starts; key decisions are distilled into the parent story's * Decisions at close, but the plan itself stays — it is the historical record of what we did.)

Manual QA scenarios (scaffolded via compass add test_scenario) that verify this task. Link new ones here as they're created; the scenario doc itself links back via its "Verifies task" field.

Abandoned at sprint 25 close. Sprint 26 replaces the codegen approaches tried so far with one method: for each module, sync codegen and clear its drift. Sprint 26 opens new, clean stories for each module. This story is not carried forward.