fix(mcpd): anthropic adapter supports OAuth (sk-ant-oat) keys via Bearer

Claude subscription / Claude Code keys are OAuth tokens and authenticate with
Authorization: Bearer, not x-api-key. mcpd's server adapter only sent x-api-key,
so registering an OAuth key as a fallback Llm 401'd ("invalid x-api-key").
Mirror the mcplocal client adapter's isOAuth switch so an OAuth key works as a
server-side anthropic fallback.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/mcpd/src/services/llm/adapters/anthropic.ts

@@ -182,9 +182,15 @@ export class AnthropicAdapter implements LlmAdapter {
   }
 
   private headers(ctx: InferContext): Record<string, string> {
+    // Claude subscription / Claude Code keys are OAuth tokens (`sk-ant-oat…`)
+    // and authenticate via Bearer, not x-api-key — mirror the mcplocal client
+    // adapter so an OAuth key works as a server-side fallback Llm.
+    const isOAuth = ctx.apiKey.startsWith('sk-ant-oat');
     return {
       'Content-Type': 'application/json',
-      'x-api-key': ctx.apiKey,
+      ...(isOAuth
+        ? { Authorization: `Bearer ${ctx.apiKey}` }
+        : { 'x-api-key': ctx.apiKey }),
       'anthropic-version': ANTHROPIC_VERSION,
     };
   }