Preserve preview harness, editor, email and task improvements

Snapshot current maintainer-preview application changes and regression fixtures for integration into lab. Excludes local runtime data, evaluation outputs and source backups. Focused Python regression selection: 140 passed; full suite not certified.

src/agent_runs.py

@@ -24,7 +24,7 @@ logger = logging.getLogger(__name__)
 
 
 class _Run:
-    __slots__ = ("buffer", "subscribers", "status", "task", "evict_task", "run_id")
+    __slots__ = ("buffer", "subscribers", "status", "task", "evict_task", "run_id", "finish_requested", "finish_event")
 
     def __init__(self) -> None:
         self.buffer: list = []          # ordered SSE event strings (replay log)
@@ -35,6 +35,8 @@ class _Run:
         # Stable across every subscription/replay of this exact detached run.
         # The browser uses it to make local cost accounting replay-idempotent.
         self.run_id: str = uuid.uuid4().hex
+        self.finish_requested: bool = False
+        self.finish_event = asyncio.Event()
 
 
 _RUNS: Dict[str, _Run] = {}
@@ -279,3 +281,25 @@ def stop(session_id: str, expected_run_id: Optional[str] = None) -> bool:
         run.task.cancel()
         return True
     return False
+
+
+def request_finish(session_id: str, expected_run_id: Optional[str] = None) -> bool:
+    """Ask the exact active run to finish after its completed editor work."""
+    run = _RUNS.get(session_id)
+    if not expected_run_id or run is None or run.run_id != expected_run_id:
+        return False
+    if run.status != "running" or not run.task or run.task.done():
+        return False
+    run.finish_requested = True
+    run.finish_event.set()
+    return True
+
+
+def should_finish(session_id: str) -> bool:
+    run = _RUNS.get(session_id)
+    return bool(run and run.status == "running" and run.finish_requested)
+
+
+def get_finish_event(session_id: str) -> Optional[asyncio.Event]:
+    run = _RUNS.get(session_id)
+    return run.finish_event if run and run.status == "running" else None