fix: URL-based auth for third-party Anthropic endpoints + CI test fixes (#4148)

* fix(tests): mock sys.stdin.isatty for cmd_model TTY guard

* fix(tests): update camofox snapshot format + trajectory compressor mock path

- test_browser_camofox: mock response now uses snapshot format (accessibility tree)
- test_trajectory_compressor: mock _get_async_client instead of setting async_client directly

* fix: URL-based auth detection for third-party Anthropic endpoints + test fixes

Reverts the key-prefix approach from #4093 which broke JWT and managed
key OAuth detection. Instead, detects third-party endpoints by URL:
if base_url is set and isn't anthropic.com, it's a proxy (Azure AI
Foundry, AWS Bedrock, etc.) that uses x-api-key regardless of key format.

Auth decision chain is now:
1. _requires_bearer_auth(url) → MiniMax → Bearer
2. _is_third_party_anthropic_endpoint(url) → Azure/Bedrock → x-api-key
3. _is_oauth_token(key) → OAuth on direct Anthropic → Bearer
4. else → x-api-key

Also includes test fixes from PR #4051 by @erosika:
- Mock sys.stdin.isatty for cmd_model TTY guard
- Update camofox snapshot format mock
- Fix trajectory compressor async client mock path

---------

Co-authored-by: Erosika <eri@plasticlabs.ai>

tests/test_trajectory_compressor.py

@@ -405,12 +405,13 @@ class TestGenerateSummary:
     @pytest.mark.asyncio
     async def test_generate_summary_async_handles_none_content(self):
         tc = _make_compressor()
-        tc.async_client = MagicMock()
-        tc.async_client.chat.completions.create = AsyncMock(
+        mock_client = MagicMock()
+        mock_client.chat.completions.create = AsyncMock(
             return_value=SimpleNamespace(
                 choices=[SimpleNamespace(message=SimpleNamespace(content=None))]
             )
         )
+        tc._get_async_client = MagicMock(return_value=mock_client)
         metrics = TrajectoryMetrics()
 
         summary = await tc._generate_summary_async("Turn content", metrics)