Post categorized watcher results from early host completion evidence

- update the categorized watcher to use the latest matching host reporter artifact written before grouped finalization so grouped results can be posted as soon as the host run is actually done
- reduce dependence on the later parent Cloud Run Finished summary block for grouped-run completion reporting
- keep grouped runs from waiting until near parent-run completion when real host-level completion evidence is already available

atvm/watcher-service/atvm_run_watcher.py

@@ -342,6 +342,29 @@ def collect_host_results(
     return results
 
 
+def collect_latest_host_result(
+    reporter_root: Path,
+    expected_hosts: List[str],
+    kernels: Dict[str, str],
+    run_started_at: datetime,
+    run_ended_at: Optional[datetime] = None,
+) -> Optional[Tuple[str, HostResult]]:
+    results = collect_host_results(
+        reporter_root=reporter_root,
+        expected_hosts=expected_hosts,
+        kernels=kernels,
+        run_started_at=run_started_at,
+        run_ended_at=run_ended_at,
+    )
+    if not results:
+        return None
+    latest = max(
+        results.items(),
+        key=lambda item: item[1].timestamp or datetime.fromtimestamp(0, tz=timezone.utc),
+    )
+    return latest
+
+
 def find_check_xml_end(
     reporter_root: Path,
     started_at: datetime,
@@ -748,6 +771,19 @@ def discover_categorized_subruns(
             if summary and (not host_results or all(result.host == "check-xml-files" for result in host_results.values())):
                 host_results = summary["host_results"]
                 completed_hosts.extend([host for host in host_results if host not in completed_hosts])
+            if not host_results and check_ts:
+                latest_host = collect_latest_host_result(
+                    reporter_root=reporter_root,
+                    expected_hosts=expected_hosts,
+                    kernels=inventory,
+                    run_started_at=started_at,
+                    run_ended_at=check_ts + timedelta(seconds=5),
+                )
+                if latest_host:
+                    host, result = latest_host
+                    host_results = {host: result}
+                    if host not in completed_hosts:
+                        completed_hosts.append(host)
             if summary:
                 current_summary_index += 1
             state = "RUNNING"
@@ -763,6 +799,8 @@ def discover_categorized_subruns(
                 notes.append("Final `check-xml-files.ts` validation passed.")
             if summary and host_results:
                 notes.append("Host result details were derived from the parent categorized run log summary.")
+            elif host_results and check_ts:
+                notes.append("Host result details were derived from the latest matching host reporter artifact written before grouped finalization.")
             elif check_ts and not host_results and parent_active:
                 notes.append("Grouped reporter XML arrived before the parent run log exposed the final host summary; waiting to post until host details are available.")
             if display_name != raw_display_name: