Fix type annotations for sentinel values in job manager (#6349)

Add `type[DEFAULT]` to type annotations for parameters that use the
DEFAULT sentinel value. This fixes runtime type checking failures with
typeguard when sentinel values are passed as arguments.

Use explicit type casts and restructured parameter passing to satisfy
mypy's type narrowing requirements. The sentinel pattern allows
distinguishing between "parameter not provided" and "parameter
explicitly set to None", which is critical for job management logic.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <[email protected]>

Author: agners

supervisor/jobs/__init__.py

@@ -9,7 +9,7 @@
 from dataclasses import dataclass
 from datetime import datetime
 import logging
-from typing import Any, Self
+from typing import Any, Self, cast
 from uuid import uuid4
 
 from attr.validators import gt, lt
@@ -196,7 +196,7 @@ def update(
         self,
         progress: float | None = None,
         stage: str | None = None,
-        extra: dict[str, Any] | None = DEFAULT,  # type: ignore
+        extra: dict[str, Any] | None | type[DEFAULT] = DEFAULT,
         done: bool | None = None,
     ) -> None:
         """Update multiple fields with one on change event."""
@@ -207,8 +207,8 @@ def update(
             self.progress = progress
         if stage is not None:
             self.stage = stage
-        if extra != DEFAULT:
-            self.extra = extra
+        if extra is not DEFAULT:
+            self.extra = cast(dict[str, Any] | None, extra)
 
         # Done has special event. use that to trigger on change if included
         # If not then just use any other field to trigger
@@ -306,19 +306,21 @@ def new_job(
         reference: str | None = None,
         initial_stage: str | None = None,
         internal: bool = False,
-        parent_id: str | None = DEFAULT,  # type: ignore
+        parent_id: str | None | type[DEFAULT] = DEFAULT,
         child_job_syncs: list[ChildJobSyncFilter] | None = None,
     ) -> SupervisorJob:
         """Create a new job."""
-        job = SupervisorJob(
-            name,
-            reference=reference,
-            stage=initial_stage,
-            on_change=self._on_job_change,
-            internal=internal,
-            child_job_syncs=child_job_syncs,
-            **({} if parent_id == DEFAULT else {"parent_id": parent_id}),  # type: ignore
-        )
+        kwargs: dict[str, Any] = {
+            "reference": reference,
+            "stage": initial_stage,
+            "on_change": self._on_job_change,
+            "internal": internal,
+            "child_job_syncs": child_job_syncs,
+        }
+        if parent_id is not DEFAULT:
+            kwargs["parent_id"] = parent_id
+
+        job = SupervisorJob(name, **kwargs)
 
         # Shouldn't happen but inability to find a parent for progress reporting
         # shouldn't raise and break the active job