fix(brain): recover colon-JSON and single tool_call object forms

qwen2.5:3b emits tool calls in text shapes the parser dropped, breaking
two reviewer-reported behaviours:

- `getWeather: {"location": "Seoul"}` (a JSON object after the colon) was
  dumped wholesale into {"query": "{...}"}, so `location` never reached the
  tool. getWeather then ran with empty args, returned the auto-detected
  location's weather, the model noticed the mismatch and retried — looping up
  to 8 times before giving up with an English error. Now the JSON object after
  the colon is parsed directly as the argument dict.
- `call_stop: {"id":..., "function": {"name": "setBroadcast",
  "arguments": "{\"action\": \"stop\"}"}}` — a single tool_call object without
  the `tool_calls: [...]` array wrapper, behind a `call_xxx:` label — matched
  no form, so the raw JSON leaked to the user AND setBroadcast never ran
  ("방송 꺼줘" did nothing). Now name + arguments are pulled from the embedded
  `function` object when the name is in the allow-list.

Field-captured from the live qwen2.5:3b brain (2026-06-12). Tests cover both
shapes, non-ASCII args, dict/string arguments, and unknown-tool rejection.

tests/test_text_tool_call_parser.py

@@ -84,6 +84,75 @@ class TestSimplifiedColonForm:
         assert name is None
 
 
+class TestColonFormWithJsonObjectValue:
+    """Form 2b: `toolName: {json object}`.
+
+    Field-captured from qwen2.5:3b (2026-06-12): the model emits the weather
+    call as ``getWeather: {"location": "Seoul"}``. The whole JSON object must
+    become the argument dict. Before the fix it was dumped into
+    ``{"query": "{...}"}``, so ``location`` never reached the tool, the tool
+    fell back to the auto-detected location, and the model looped retrying
+    different cities until the turn cap (observed: 8 getWeather calls, then an
+    English error fallback).
+    """
+
+    def test_json_object_after_colon_becomes_args(self):
+        content = 'getWeather: {"location": "Seoul"}'
+        name, args, _ = _extract(content, tool_name="getWeather")
+        assert name == "getWeather"
+        assert args.get("location") == "Seoul"
+        assert "query" not in args
+
+    def test_empty_json_object_after_colon(self):
+        content = "getWeather: {}"
+        name, args, _ = _extract(content, tool_name="getWeather")
+        assert name == "getWeather"
+        assert args == {}
+
+    def test_non_ascii_location_after_colon(self):
+        content = 'getWeather: {"location": "서울"}'
+        name, args, _ = _extract(content, tool_name="getWeather")
+        assert name == "getWeather"
+        assert args.get("location") == "서울"
+
+
+class TestSingleToolCallObjectForm:
+    """Form 2c: a single tool_call object without the `tool_calls: [...]` array.
+
+    Field-captured from qwen2.5:3b (2026-06-12) on "방송 꺼줘": the model picked
+    the right tool but emitted it behind a `call_xxx:` label as a bare object.
+    The name + arguments must be pulled from the embedded ``function`` object;
+    before the fix this leaked the raw JSON to the user and the tool never ran.
+    """
+
+    def test_single_object_with_string_arguments(self):
+        content = (
+            'call_stop: {"id": "call_stop", "type": "function", '
+            '"function": {"name": "setBroadcast", '
+            '"arguments": "{\\"action\\": \\"stop\\"}"}}'
+        )
+        name, args, _ = _extract(content, tool_name="setBroadcast")
+        assert name == "setBroadcast"
+        assert args.get("action") == "stop"
+
+    def test_single_object_with_dict_arguments(self):
+        content = (
+            '{"id": "c1", "type": "function", '
+            '"function": {"name": "getWeather", "arguments": {"location": "Seoul"}}}'
+        )
+        name, args, _ = _extract(content, tool_name="getWeather")
+        assert name == "getWeather"
+        assert args.get("location") == "Seoul"
+
+    def test_single_object_rejects_unknown_tool(self):
+        content = (
+            '{"function": {"name": "fileSystem_write", '
+            '"arguments": "{\\"path\\": \\"/tmp/x\\"}"}}'
+        )
+        name, _args, _ = _extract(content, tool_name="setBroadcast")
+        assert name is None
+
+
 class TestFunctionCallForm:
     """Form 3: `toolName(...)`."""