Anchor generated attachments to assistant messages

Deliverables now inherit the active assistant draft message ID so clients can render them beside the reply that produced them.

docs/PROTOCOL.md

@@ -309,7 +309,7 @@ adapter-managed storage and broadcasts:
     "kind": "image" | "voice" | "video" | "audio" | "document",
     "inline_image": false,
     "conversation_id": "a1b2…",
-    "message_id": null,
+    "message_id": "draft-8c1f…" | null,
     "created_at": "2026-09-02T18:30:00+00:00",
     "expires_at": "2026-09-09T18:30:00+00:00",     // null when retention=0
     "download_path": "/attachments/e5f6…" },

plugin/pheby/adapter.py

@@ -379,11 +379,18 @@ class PhebyAdapter(BasePlatformAdapter):
         return SendResult(success=True, message_id=clarify_id)
 
     # ── deliverables (attachments) ───────────────────────────────────────
+    def _active_assistant_message_id(self, conversation_id: str) -> Optional[str]:
+        """Return the live assistant draft that a deliverable belongs beneath."""
+        draft = self._drafts.get(conversation_id)
+        message_id = draft.get("message_id") if isinstance(draft, dict) else None
+        return str(message_id) if message_id else None
+
     async def _register_and_broadcast(
         self,
         file_path: str,
         conversation_id: str,
         *,
+        message_id: Optional[str] = None,
         kind_hint: Optional[str] = None,
         filename: Optional[str] = None,
     ) -> Optional[Dict[str, Any]]:
@@ -392,7 +399,7 @@ class PhebyAdapter(BasePlatformAdapter):
         desc = await self._server.store.register_file(
             file_path,
             conversation_id=conversation_id,
-            message_id=None,
+            message_id=message_id or self._active_assistant_message_id(conversation_id),
             filename=filename,
             kind_hint=kind_hint,
         )

tests/test_pheby.py

@@ -28,6 +28,7 @@ if str(_PLUGIN_DIR) not in sys.path:
 
 from pheby import protocol as proto  # noqa: E402
 from pheby.attachments import AttachmentStore, constant_time_equals  # noqa: E402
+from pheby.adapter import PhebyAdapter  # noqa: E402
 from pheby.config import load_config  # noqa: E402
 from pheby.conversations import ConversationRouter  # noqa: E402
 from pheby.server import PhebyServer  # noqa: E402
@@ -344,6 +345,13 @@ class TestConversations:
 # Attachments
 # ═══════════════════════════════════════════════════════════════════════════
 class TestAttachments:
+    def test_adapter_anchors_deliverable_to_active_assistant_draft(self):
+        adapter = object.__new__(PhebyAdapter)
+        adapter._drafts = {"conv": {"message_id": "draft-run-1", "text": ""}}
+
+        assert adapter._active_assistant_message_id("conv") == "draft-run-1"
+        assert adapter._active_assistant_message_id("unknown") is None
+
     @pytest.mark.asyncio
     async def test_register_describe_download_path(self, tmp_path):
         src = Path(tmp_path) / "report.pdf"