Fix OAuth authentication by using claude_code_oauth_token parameter

- Extract access token from credentials JSON in prepare.ts
- Pass token to base action via claude_code_oauth_token parameter
- Remove unused OAuth setup code and CLAUDE_CREDENTIALS env var
- This uses the official base action's OAuth support correctly

src/entrypoints/prepare.ts

@@ -18,7 +18,6 @@ import { createPrompt } from "../create-prompt";
 import { createClient } from "../github/api/client";
 import { fetchGitHubData } from "../github/data/fetcher";
 import { parseGitHubContext } from "../github/context";
-import { setupOAuthCredentials } from "../claude/oauth-setup";
 
 async function run() {
   try {
@@ -28,10 +27,19 @@ async function run() {
 
     // Check if OAuth credentials are provided and API key is empty (OAuth mode)
     if (claudeCredentials && !anthropicApiKey) {
-      await setupOAuthCredentials(claudeCredentials);
-      console.log(
-        "OAuth credentials configured for Claude AI Max subscription",
-      );
+      // Parse the credentials to extract the access token
+      try {
+        const parsedCredentials = JSON.parse(claudeCredentials);
+        if (parsedCredentials.claudeAiOauth?.accessToken) {
+          // Output the access token for the base action to use
+          core.setOutput("claude_oauth_token", parsedCredentials.claudeAiOauth.accessToken);
+          console.log("OAuth access token extracted for Claude AI Max subscription");
+        } else {
+          throw new Error("Invalid credentials format: missing claudeAiOauth.accessToken");
+        }
+      } catch (error) {
+        throw new Error(`Failed to parse OAuth credentials: ${error instanceof Error ? error.message : String(error)}`);
+      }
     }
 
     // Step 2: Setup GitHub token