fix(parser): parse Gemma 3/4 custom tool calling tokens (#5033)

* fix: parse Gemma 3/4 custom tool calling tokens in parser

* test: cover Gemma tool call parsing

---------

Co-authored-by: Alexandre Teixeira <alexandremagteixeira@gmail.com>

tests/test_gemma_tool_call_parsing.py

@@ -0,0 +1,39 @@
+from src.agent_tools import parse_tool_blocks, strip_tool_blocks
+
+
+def test_gemma_tool_call_json_args_parse_and_strip():
+    raw = '<|tool_call|>call:web_search{"query":"hello world"}<|tool_call|>'
+
+    blocks = parse_tool_blocks(raw)
+
+    assert len(blocks) == 1
+    assert blocks[0].tool_type == "web_search"
+    assert blocks[0].content == "hello world"
+    assert strip_tool_blocks(raw).strip() == ""
+
+
+def test_gemma_tool_call_unquoted_args_parse():
+    raw = '<|tool_call|>call:web_search{query: "hello world"}<|tool_call|>'
+
+    blocks = parse_tool_blocks(raw)
+
+    assert len(blocks) == 1
+    assert blocks[0].tool_type == "web_search"
+    assert blocks[0].content == "hello world"
+
+
+def test_gemma_tool_call_normalizes_dash_tool_name():
+    raw = '<|tool_call|>call:read-file{"path":"README.md"}<|tool_call|>'
+
+    blocks = parse_tool_blocks(raw)
+
+    assert len(blocks) == 1
+    assert blocks[0].tool_type == "read_file"
+    assert blocks[0].content == "README.md"
+
+
+def test_gemma_parser_does_not_strip_non_tool_fenced_metadata():
+    raw = '```python id="abc"\nprint("hello")\n```'
+
+    assert parse_tool_blocks(raw) == []
+    assert strip_tool_blocks(raw) == raw