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/agent/test_auxiliary_client.py

@@ -310,7 +310,7 @@ class TestExpiredCodexFallback:
     def test_hermes_oauth_file_sets_oauth_flag(self, monkeypatch):
         """OAuth-style tokens should get is_oauth=True (token is not sk-ant-api-*)."""
         # Mock resolve_anthropic_token to return an OAuth-style token
-        with patch("agent.anthropic_adapter.resolve_anthropic_token", return_value="sk-ant-oat01-hermes-oauth-test"), \
+        with patch("agent.anthropic_adapter.resolve_anthropic_token", return_value="hermes-oauth-jwt-token"), \
              patch("agent.anthropic_adapter.build_anthropic_client") as mock_build:
             mock_build.return_value = MagicMock()
             from agent.auxiliary_client import _try_anthropic, AnthropicAuxiliaryClient
@@ -364,7 +364,7 @@ class TestExpiredCodexFallback:
 
     def test_claude_code_oauth_env_sets_flag(self, monkeypatch):
         """CLAUDE_CODE_OAUTH_TOKEN env var should get is_oauth=True."""
-        monkeypatch.setenv("CLAUDE_CODE_OAUTH_TOKEN", "sk-ant-oat01-cc-oauth-test")
+        monkeypatch.setenv("CLAUDE_CODE_OAUTH_TOKEN", "cc-oauth-token-test")
         monkeypatch.delenv("ANTHROPIC_TOKEN", raising=False)
         with patch("agent.anthropic_adapter.build_anthropic_client") as mock_build:
             mock_build.return_value = MagicMock()