sched: add schedule models, file store, and deployment revisions (T07)

src/wf_artifacts/models.py

@@ -222,6 +222,14 @@ class WorkflowDeployment(BaseModel):
         default_factory=list
     )
     drift_policy: DriftPolicy = DriftPolicy.BLOCK
+    revision: int = Field(
+        default=1,
+        ge=1,
+        description=(
+            "Mutable deployment revision for edit-race rechecks. "
+            "Incremented on every save; admission freezes the revision it saw."
+        ),
+    )
 
     def binding_map(self) -> dict[str, str]:
         """Return bindings keyed by dot-joined logical source ref."""