fix(anthropic): remove Claude Code fingerprinting from OAuth Messages API path (#16957)

* fix(anthropic): remove Claude Code fingerprinting from OAuth Messages API path

OAuth requests now identify as Hermes on the wire. Removed:

  - "You are Claude Code, Anthropic's official CLI for Claude." system
    prompt prepend
  - Hermes Agent → Claude Code / Nous Research → Anthropic
    system-prompt substitutions
  - mcp_ tool-name prefix on outgoing tool schemas + message history
  - Matching mcp_ strip on inbound tool_use blocks (strip_tool_prefix path
    removed from AnthropicTransport.normalize_response, + all 5 call
    sites in run_agent.py and auxiliary_client.py)
  - user-agent: claude-cli/<v> (external, cli) and x-app: cli headers on
    the Messages API client

Added:

  - OAuth path strips context-1m-2025-08-07 — Anthropic rejects OAuth
    requests carrying it with HTTP 400 'This authentication style is
    incompatible with the long context beta header.'

Kept (auth plumbing, not identity spoofing):

  - _is_oauth_token classifier and is_oauth flag threading
  - Bearer vs x-api-key auth routing
  - _OAUTH_ONLY_BETAS (claude-code-20250219, oauth-2025-04-20) — backend
    requires these on the OAuth-gated Messages endpoint
  - _OAUTH_CLIENT_ID (Claude Code's) — Anthropic doesn't issue OAuth
    creds to third parties; this is the only way the login flow works
  - claude-cli/<v> User-Agent on the OAuth token exchange + refresh
    endpoints at platform.claude.com/v1/oauth/token — bare requests get
    Cloudflare 1010 blocked

Verified live against api.anthropic.com with a fresh sk-ant-oat01-*
token:

  - claude-haiku-4-5 simple message: HTTP 200, 'OK' response
  - claude-haiku-4-5 tool call: HTTP 200, stop_reason=tool_use, tool
    named 'terminal' (no mcp_ prefix) round-tripped correctly
  - Outgoing wire: no user-agent, no x-app, real Hermes identity in
    system prompt, real tool name in schema

Closes/supersedes #16820 (mcp_ PascalCase normalization patch — no longer
needed since the mcp_ round-trip is gone).

* fix(anthropic): resolve_anthropic_token() reads credential pool first

Close the gap where ~/.hermes/auth.json → credential_pool.anthropic
(where hermes login + dashboard PKCE flow write OAuth tokens) was not
in resolve_anthropic_token()'s source list.

Before: users who authed via hermes login got the token written into
the pool, but legacy fallback code paths (auxiliary_client, models
catalog fetch, explicit-runtime path) that call resolve_anthropic_token()
saw None and raised 'No Anthropic credentials found' — even though the
token was sitting in auth.json.

New priority 1: pool.select() with env-sourced entries skipped. Skipping
env:* entries preserves the existing env-var priority logic further
down the chain (static env OAuth → refreshable Claude Code upgrade via
_prefer_refreshable_claude_code_token).

Surfaced while writing the hermes-agent-dev skill playbook for
'finding a live OAuth token for an E2E test'.

---------

Co-authored-by: teknium1 <teknium@users.noreply.github.com>

run_agent.py

@@ -9706,7 +9706,7 @@ class AIAgent:
                                    is_oauth=self._is_anthropic_oauth,
                                    preserve_dots=self._anthropic_preserve_dots())
                     summary_response = self._anthropic_messages_create(_ant_kw)
-                    _summary_result = _tsum.normalize_response(summary_response, strip_tool_prefix=self._is_anthropic_oauth)
+                    _summary_result = _tsum.normalize_response(summary_response)
                     final_response = (_summary_result.content or "").strip()
                 else:
                     summary_response = self._ensure_primary_openai_client(reason="iteration_limit_summary").chat.completions.create(**summary_kwargs)
@@ -9736,7 +9736,7 @@ class AIAgent:
                                     max_tokens=self.max_tokens, reasoning_config=self.reasoning_config,
                                     preserve_dots=self._anthropic_preserve_dots())
                     retry_response = self._anthropic_messages_create(_ant_kw2)
-                    _retry_result = _tretry.normalize_response(retry_response, strip_tool_prefix=self._is_anthropic_oauth)
+                    _retry_result = _tretry.normalize_response(retry_response)
                     final_response = (_retry_result.content or "").strip()
                 else:
                     summary_kwargs = {
@@ -10852,12 +10852,7 @@ class AIAgent:
                         # would have been appended in the non-truncated path.
                         _trunc_msg = None
                         _trunc_transport = self._get_transport()
-                        if self.api_mode == "anthropic_messages":
-                            _trunc_result = _trunc_transport.normalize_response(
-                                response, strip_tool_prefix=self._is_anthropic_oauth
-                            )
-                        else:
-                            _trunc_result = _trunc_transport.normalize_response(response)
+                        _trunc_result = _trunc_transport.normalize_response(response)
                         _trunc_msg = _trunc_result
 
                         _trunc_content = getattr(_trunc_msg, "content", None) if _trunc_msg else None
@@ -12195,10 +12190,7 @@ class AIAgent:
 
             try:
                 _transport = self._get_transport()
-                _normalize_kwargs = {}
-                if self.api_mode == "anthropic_messages":
-                    _normalize_kwargs["strip_tool_prefix"] = self._is_anthropic_oauth
-                normalized = _transport.normalize_response(response, **_normalize_kwargs)
+                normalized = _transport.normalize_response(response)
                 assistant_message = normalized
                 finish_reason = normalized.finish_reason