fix(mcp): make get_note / get_task share-aware

The injected menu tells the agent to open any hit with get_note(id), and
that menu can list a collaborator's record reached through a shared
project. The fetch was still owner-only, so those lines answered
"not found" — for a record the same user opens fine in the browser.
The agent path was strictly narrower than the web path for the same id.

Same boundary miss as #2093: the list side was widened for sharing, the
fetch side wasn't. Both tools now resolve through get_note_for_user,
apply the trash filter themselves (permission resolution says nothing
about liveness), and attach describe_provenance so a shared record
arrives marked as someone else's rather than passing as the caller's.

routes/tasks.py's parent-title lookup had the same narrowness: a shared
subtask rendered as an orphan when its parent was equally shared.

Four fetch tests across three files were patching notes_svc.get_note and
had to be retargeted — note 2109's third sub-case, caught by grepping
tests/ for the old name before pushing rather than by CI (#2159).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RLwAaV4DQEmVyn496HnEvt

src/scribe/routes/tasks.py

@@ -11,7 +11,6 @@ from scribe.services import systems as systems_svc
 from scribe.services.embeddings import upsert_note_embedding
 from scribe.services.notes import (
     create_note,
-    get_note,
     get_note_for_user,
     list_notes,
     update_note,
@@ -187,8 +186,10 @@ async def get_task_route(task_id: int):
     data = task.to_dict()
     data["permission"] = permission
     if task.parent_id:
-        parent = await get_note(uid, task.parent_id)
-        data["parent_title"] = parent.title if parent else None
+        # Share-aware like the task itself: a shared subtask whose parent is also
+        # shared would otherwise render as an orphan with no parent title.
+        parent = await get_note_for_user(uid, task.parent_id)
+        data["parent_title"] = parent[0].title if parent else None
     data["systems"] = [s.to_dict() for s in await systems_svc.list_record_systems(uid, task_id)]
     return jsonify(data)