fix(agent): include name field on every role:tool message for Gemini compatibility (#16478)

Gemini's OpenAI-compatibility endpoint strictly requires the `name` field
on `role: tool` messages — it returns HTTP 400 ("Request contains an
invalid argument") when the function name is missing. OpenAI/Anthropic/
ollama tolerate the absence, so the gap stays invisible until the
conversation accumulates a tool turn and the user routes it through Gemini
(direct API or via ollama-cloud proxy).

Fix: add a `_get_tool_call_name_static()` helper alongside the existing
`_get_tool_call_id_static()`, and populate `name` at every site that
constructs a `role: tool` message — the pre-call sanitizer stub, the
tool-call args repair marker, both interrupt-skip paths, both
result-append paths (parallel + sequential), the invalid-tool-name
recovery, the invalid-JSON-args recovery, and the exception fallback.

Each call site was already in scope of the function name (`function_name`,
`skipped_name`, `name`, or a dict tool_call), so the change is local —
no new lookups, no behavior change for providers that already worked.

Fixes #16478

tests/run_agent/test_tool_call_args_sanitizer.py

@@ -96,6 +96,7 @@ def test_marker_message_inserted_when_missing():
     assert repaired == 1
     assert messages[1] == {
         "role": "tool",
+        "name": "read_file",
         "tool_call_id": "call_1",
         "content": marker,
     }