feat: native Anthropic provider with Claude Code credential auto-discovery

Add Anthropic as a first-class inference provider, bypassing OpenRouter
for direct API access. Uses the native Anthropic SDK with a full format
adapter (same pattern as the codex_responses api_mode).

## Auth (three methods, priority order)
1. ANTHROPIC_API_KEY env var (regular API key, sk-ant-api-*)
2. ANTHROPIC_TOKEN / CLAUDE_CODE_OAUTH_TOKEN env var (setup-token, sk-ant-oat-*)
3. Auto-discovery from ~/.claude/.credentials.json (Claude Code subscription)
   - Reads Claude Code's OAuth credentials
   - Checks token expiry with 60s buffer
   - Setup tokens use Bearer auth + anthropic-beta: oauth-2025-04-20 header
   - Regular API keys use standard x-api-key header

## Changes by file

### New files
- agent/anthropic_adapter.py — Client builder, message/tool/response
  format conversion, Claude Code credential reader, token resolver.
  Handles system prompt extraction, tool_use/tool_result blocks,
  thinking/reasoning, orphaned tool_use cleanup, cache_control.
- tests/test_anthropic_adapter.py — 36 tests covering all adapter logic

### Modified files
- pyproject.toml — Add anthropic>=0.39.0 dependency
- hermes_cli/auth.py — Add 'anthropic' to PROVIDER_REGISTRY with
  three env vars, plus 'claude'/'claude-code' aliases
- hermes_cli/models.py — Add model catalog, labels, aliases, provider order
- hermes_cli/main.py — Add 'anthropic' to --provider CLI choices
- hermes_cli/runtime_provider.py — Add Anthropic branch returning
  api_mode='anthropic_messages' (before generic api_key fallthrough)
- hermes_cli/setup.py — Add Anthropic setup wizard with Claude Code
  credential auto-discovery, model selection, OpenRouter tools prompt
- agent/auxiliary_client.py — Add claude-haiku-4-5 as aux model
- agent/model_metadata.py — Add bare Claude model context lengths
- run_agent.py — Add anthropic_messages api_mode:
  * Client init (Anthropic SDK instead of OpenAI)
  * API call dispatch (_anthropic_client.messages.create)
  * Response validation (content blocks)
  * finish_reason mapping (stop_reason -> finish_reason)
  * Token usage (input_tokens/output_tokens)
  * Response normalization (normalize_anthropic_response)
  * Client interrupt/rebuild
  * Prompt caching auto-enabled for native Anthropic
- tests/test_run_agent.py — Update test_anthropic_base_url_accepted to
  expect native routing, add test_prompt_caching_native_anthropic

tests/test_run_agent.py

@@ -281,20 +281,21 @@ class TestMaskApiKey:
 
 class TestInit:
     def test_anthropic_base_url_accepted(self):
-        """Anthropic base URLs should be accepted (OpenAI-compatible endpoint)."""
+        """Anthropic base URLs should route to native Anthropic client."""
         with (
             patch("run_agent.get_tool_definitions", return_value=[]),
             patch("run_agent.check_toolset_requirements", return_value={}),
-            patch("run_agent.OpenAI") as mock_openai,
+            patch("agent.anthropic_adapter._anthropic_sdk") as mock_anthropic,
         ):
-            AIAgent(
+            agent = AIAgent(
                 api_key="test-key-1234567890",
                 base_url="https://api.anthropic.com/v1/",
                 quiet_mode=True,
                 skip_context_files=True,
                 skip_memory=True,
             )
-            mock_openai.assert_called_once()
+            assert agent.api_mode == "anthropic_messages"
+            mock_anthropic.Anthropic.assert_called_once()
 
     def test_prompt_caching_claude_openrouter(self):
         """Claude model via OpenRouter should enable prompt caching."""
@@ -345,6 +346,23 @@ class TestInit:
             )
             assert a._use_prompt_caching is False
 
+    def test_prompt_caching_native_anthropic(self):
+        """Native Anthropic provider should enable prompt caching."""
+        with (
+            patch("run_agent.get_tool_definitions", return_value=[]),
+            patch("run_agent.check_toolset_requirements", return_value={}),
+            patch("agent.anthropic_adapter._anthropic_sdk"),
+        ):
+            a = AIAgent(
+                api_key="test-key-1234567890",
+                base_url="https://api.anthropic.com/v1/",
+                quiet_mode=True,
+                skip_context_files=True,
+                skip_memory=True,
+            )
+            assert a.api_mode == "anthropic_messages"
+            assert a._use_prompt_caching is True
+
     def test_valid_tool_names_populated(self):
         """valid_tool_names should contain names from loaded tools."""
         tools = _make_tool_defs("web_search", "terminal")