fix: promote deferred tools after tool_search returns schema (#1570)

* fix: promote matched tools from deferred registry after tool_search returns schema

After tool_search returns a tool's full schema, the tool is promoted
(removed from the deferred registry) so DeferredToolFilterMiddleware
stops filtering it from bind_tools on subsequent LLM calls.

Without this, deferred tools are permanently filtered — the LLM gets
the schema from tool_search but can never invoke the tool because
the middleware keeps stripping it.

Fixes #1554

* test: add promote() and tool_search promotion tests

Tests cover:
- promote removes tools from registry
- promote nonexistent/empty is no-op
- search returns nothing after promote
- middleware passes promoted tools through
- tool_search auto-promotes matched tools (select + keyword)

* fix: address review — lint blank line + empty registry guard

- Add missing blank line between FakeRequest methods (E301)
- Use 'if not registry' to handle empty registries consistently

---------

Co-authored-by: d 🔹 <258577966+voidborne-d@users.noreply.github.com>
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>

backend/packages/harness/deerflow/tools/builtins/tool_search.py

@@ -51,6 +51,21 @@ class DeferredToolRegistry:
             )
         )
 
+    def promote(self, names: set[str]) -> None:
+        """Remove tools from the deferred registry so they pass through the filter.
+
+        Called after tool_search returns a tool's schema — the LLM now knows
+        the full definition, so the DeferredToolFilterMiddleware should stop
+        stripping it from bind_tools on subsequent calls.
+        """
+        if not names:
+            return
+        before = len(self._entries)
+        self._entries = [e for e in self._entries if e.name not in names]
+        promoted = before - len(self._entries)
+        if promoted:
+            logger.debug(f"Promoted {promoted} tool(s) from deferred to active: {names}")
+
     def search(self, query: str) -> list[BaseTool]:
         """Search deferred tools by regex pattern against name + description.
 
@@ -160,7 +175,7 @@ def tool_search(query: str) -> str:
         Matched tool definitions as JSON array.
     """
     registry = get_deferred_registry()
-    if registry is None:
+    if not registry:
         return "No deferred tools available."
 
     matched_tools = registry.search(query)
@@ -171,4 +186,8 @@ def tool_search(query: str) -> str:
     # This is model-agnostic: all LLMs understand this standard schema.
     tool_defs = [convert_to_openai_function(t) for t in matched_tools[:MAX_RESULTS]]
 
+    # Promote matched tools so the DeferredToolFilterMiddleware stops filtering
+    # them from bind_tools — the LLM now has the full schema and can invoke them.
+    registry.promote({t.name for t in matched_tools[:MAX_RESULTS]})
+
     return json.dumps(tool_defs, indent=2, ensure_ascii=False)