fix(anthropic): address gaps found in deep-dive audit

After studying clawdbot (OpenClaw) and OpenCode implementations:

## Beta headers
- Add interleaved-thinking-2025-05-14 and fine-grained-tool-streaming-2025-05-14
  as common betas (sent with ALL auth types, not just OAuth)
- OAuth tokens additionally get oauth-2025-04-20
- API keys now also get the common betas (previously got none)

## Vision/image support
- Add _convert_vision_content() to convert OpenAI multimodal format
  (image_url blocks) to Anthropic format (image blocks with base64/url source)
- Handles both data: URIs (base64) and regular URLs

## Role alternation enforcement
- Anthropic strictly rejects consecutive same-role messages (400 error)
- Add post-processing step that merges consecutive user/assistant messages
- Handles string, list, and mixed content types during merge

## Tool choice support
- Add tool_choice parameter to build_anthropic_kwargs()
- Maps OpenAI values: auto→auto, required→any, none→omit, name→tool

## Cache metrics tracking
- Anthropic uses cache_read_input_tokens / cache_creation_input_tokens
  (different from OpenRouter's prompt_tokens_details.cached_tokens)
- Add api_mode-aware branch in run_agent.py cache stats logging

## Credential refresh on 401
- On 401 error during anthropic_messages mode, re-read credentials
  via resolve_anthropic_token() (picks up refreshed Claude Code tokens)
- Rebuild client if new token differs from current one
- Follows same pattern as Codex/Nous 401 refresh handlers

## Tests
- 44 adapter tests (8 new: vision conversion, role alternation, tool choice)
- Updated beta header tests to verify new structure
- Full suite: 3198 passed, 0 regressions

run_agent.py

@@ -3830,9 +3830,15 @@ class AIAgent:
                         
                         # Log cache hit stats when prompt caching is active
                         if self._use_prompt_caching:
-                            details = getattr(response.usage, 'prompt_tokens_details', None)
-                            cached = getattr(details, 'cached_tokens', 0) or 0 if details else 0
-                            written = getattr(details, 'cache_write_tokens', 0) or 0 if details else 0
+                            if self.api_mode == "anthropic_messages":
+                                # Anthropic uses cache_read_input_tokens / cache_creation_input_tokens
+                                cached = getattr(response.usage, 'cache_read_input_tokens', 0) or 0
+                                written = getattr(response.usage, 'cache_creation_input_tokens', 0) or 0
+                            else:
+                                # OpenRouter uses prompt_tokens_details.cached_tokens
+                                details = getattr(response.usage, 'prompt_tokens_details', None)
+                                cached = getattr(details, 'cached_tokens', 0) or 0 if details else 0
+                                written = getattr(details, 'cache_write_tokens', 0) or 0 if details else 0
                             prompt = usage_dict["prompt_tokens"]
                             hit_pct = (cached / prompt * 100) if prompt > 0 else 0
                             if not self.quiet_mode:
@@ -3882,6 +3888,19 @@ class AIAgent:
                         if self._try_refresh_nous_client_credentials(force=True):
                             print(f"{self.log_prefix}🔐 Nous agent key refreshed after 401. Retrying request...")
                             continue
+                    if (
+                        self.api_mode == "anthropic_messages"
+                        and status_code == 401
+                        and hasattr(self, '_anthropic_api_key')
+                    ):
+                        # Try re-reading Claude Code credentials (they may have been refreshed)
+                        from agent.anthropic_adapter import resolve_anthropic_token, build_anthropic_client
+                        new_token = resolve_anthropic_token()
+                        if new_token and new_token != self._anthropic_api_key:
+                            self._anthropic_api_key = new_token
+                            self._anthropic_client = build_anthropic_client(new_token)
+                            print(f"{self.log_prefix}🔐 Anthropic credentials refreshed after 401. Retrying request...")
+                            continue
 
                     retry_count += 1
                     elapsed_time = time.time() - api_start_time