sched: add durable admission record and admitted run view (T05)

src/wf_artifacts/runs/models.py

@@ -25,8 +25,13 @@ def ensure_run_id(run_id: str) -> str:
 
 
 class StoredRunStatus(StrEnum):
-    """Stopped runtime statuses supported by durable run persistence."""
+    """Durable run statuses including pre-dispatch admission.
 
+    ``ADMITTED`` marks a durably admitted run with no stopped checkpoint yet.
+    Never fabricate a checkpoint, trace, output, or step count for such runs.
+    """
+
+    ADMITTED = "admitted"
     INTERRUPTED = "interrupted"
     COMPLETED = "completed"
     FAILED = "failed"
@@ -67,12 +72,35 @@ class WorkflowRunRecord(BaseModel):
     status: StoredRunStatus
     resume_readiness: ResumeReadiness
     environment: PinnedRunEnvironment
-    latest_checkpoint_id: str = Field(pattern=RUN_ID_PATTERN)
+    latest_checkpoint_id: str | None = Field(default=None, pattern=RUN_ID_PATTERN)
     diagnostics: list[DependencyDiagnostic] = Field(default_factory=list)
     created_at: datetime
     updated_at: datetime
 
 
+class RunAdmission(BaseModel):
+    """Authoritative admission record persisted before dispatch.
+
+    The admission freezes the invocation (pinned environment, resolved input,
+    limits, deployment/schedule revisions, resolved UTC instant) under a
+    preassigned run identity. It is the recovery authority for partial
+    multi-file writes: the run view (``WorkflowRunRecord``) is materialized
+    from this same identity, and dispatch uses only the captured invocation.
+    """
+
+    model_config = ConfigDict(extra="forbid")
+
+    id: str = Field(pattern=RUN_ID_PATTERN)
+    environment: PinnedRunEnvironment
+    resolved_input: dict[str, Any]
+    max_steps: int | None = None
+    scheduled_at: datetime | None = None
+    schedule_id: str | None = None
+    schedule_revision: int | None = None
+    deployment_revision: int | None = None
+    created_at: datetime
+
+
 class VersionedCheckpointState(BaseModel):
     """Lenient read envelope for stopped-run checkpoints.