First step of the scheduled-task context's hexagonal migration: the
inner-ring model, with zero infrastructure dependencies.
- ScheduleSpec / SchedulePolicy value objects
- ScheduledTask aggregate root
- ScheduledRun aggregate
- 9 domain errors, 5 enums
Rules are migrated verbatim from their current homes, each method's
docstring citing the source line: timezone/cron/next-run calculation
from deerflow/scheduler/schedules.py, context-mode and re-arm rules from
routers/scheduled_tasks.py, and the four status-derivation rules from
app/scheduler/service.py.
Two things previously held by convention are now enforced by
construction. Validation and normalization live in __post_init__, so
building a ScheduleSpec field-by-field cannot bypass them. The skipped
tombstone is a separate factory, so it can never be written as the
transient queued row that would collide with uq_scheduled_task_run_active.
The domain does not serialize itself: mapping the stored schedule_spec
JSON in and out stays with the adapter layer, keeping Mapping[str, Any]
out of every domain signature.
Production code still runs through app/scheduler/service.py -- this
commit adds no call sites and changes no behavior.
9d0b09558e