fix(feishu): skip reaction transition on resuming stream end

Stream-end events are emitted at the end of every assistant turn. When
the agent has more tool-call rounds queued, the runner sets
`_resuming=True` on the metadata. Without a guard, every intermediate
stream end removed the OnIt reaction (the first one wins, since
`_reaction_ids.pop` empties the slot) and re-added `done_emoji`,
producing a DONE reaction after every tool call instead of only at
final completion.

Wrap the OnIt removal and `done_emoji` add in a `not _resuming` guard
so the OnIt indicator persists across tool-call rounds and DONE fires
exactly once when the agent's final response lands.

`_resuming` already flows through outbound metadata
(`nanobot/agent/loop.py:747`) and survives `_coalesce_stream_deltas`
because pure `_stream_end` messages without `_stream_delta` skip the
merge branch.

Tests:
- test_no_removal_when_resuming
- test_done_emoji_only_on_final_stream_end

nanobot/channels/feishu.py

@@ -1361,7 +1361,12 @@ class FeishuChannel(BaseChannel):
         # --- stream end: final update or fallback ---
         if meta.get("_stream_end"):
             message_id = meta.get("message_id")
-            if message_id:
+            # Only finalize the OnIt -> DONE reaction transition on the truly
+            # final stream end. _resuming=True means the agent will keep
+            # working (more tool-call rounds), so leave the reaction state
+            # in place — otherwise the OnIt indicator disappears prematurely
+            # and the DONE reaction fires after every tool call.
+            if message_id and not meta.get("_resuming"):
                 reaction_id = self._reaction_ids.pop(message_id, None)
                 if reaction_id:
                     await self._remove_reaction(message_id, reaction_id)