Merge master into unified subagent activations

Integrate master 78ae4fc2d4d8ecaebb4b674028f781a358b92cc9 after the four
independent review fixes. Keep this base update separate from those fixes
and from subsequent review changes so the integration is independently
reviewable and the observed-master checkpoint remains preserved.

Retain activation-owned execution, caller-independent local discovery,
and unconditional parent final-answer delivery. Preserve master's preset
scoped scheduling tools and all delegated-child schedule deny rules. Move
the new scheduling regression from the removed driver package into the
surviving subagent package and run it through a real Spawn activation.

Preserve master's removal of runtime invariant plugins, dependencies,
exports, and test mounts. Keep context disposal before fixture directory
cleanup. Combine Python workflow ordering with activation/catalog events
without inventing unsupported source-plane import paths.

Keep all frozen Agent Note archives byte-for-byte identical to master;
do not accept Git's automatic edits to renamed archived notes. Retain
current lifecycle and delivery facts in active documentation, repair its
links, and regenerate catalogs/persistence schemas from merged source.
All 62 master persistence roots remain; only subagent/catalog gains the
PR's external membership extension. Keep master's third-party lock graph
and update only workspace dependency changes.

Validation before this checkpoint: 683 focused tests passed, seven
Windows-only cases skipped; 2,772 archived artifacts verified. Generated
catalog and active-pair checks passed. Fresh artifact build and remaining
build-dependent documentation checks continue before publication.

scripts/smoke-python-runtime.py

@@ -1128,7 +1128,7 @@ def smoke_sdk_live() -> None:
 
 
 def assert_live_turn(label: str, result: RunResult) -> None:
-    """Require completed model tool use and the smoke sentinel on the final answer line."""
+    """Require completed model tool use and a standalone smoke acknowledgement."""
     if result.finish_reason != "completed":
         event_types = [event.get("type") for event in result.events]
         turn_end_data = next(
@@ -1145,8 +1145,7 @@ def assert_live_turn(label: str, result: RunResult) -> None:
             f"{label} turn made no model-requested tool call; "
             f"final={result.final_response!r}"
         )
-    answer_lines = result.final_response.strip().splitlines()
-    if not answer_lines or answer_lines[-1].strip() != LIVE_API_SENTINEL:
+    if not any(line.strip() == LIVE_API_SENTINEL for line in result.final_response.splitlines()):
         raise AssertionError(f"{label} turn returned {result.final_response!r}")
 
 def safe_turn_end(value: object) -> object: