Add comprehensive logging for debugging 500 errors in commit_files

- Log token type (GitHub App vs PAT) and age to detect expiration issues
- Add detailed logging at ref update step where 500 error occurs
- Capture GitHub Request ID for support tickets
- Log environment context (repo, branch, files)
- Fix error handling to throw errors instead of returning custom objects
- Pass TOKEN_CREATED_AT and GITHUB_API_URL to MCP subprocess

This will help diagnose why commit_files gets 500 errors on ref updates
while tree/commit creation succeeds.

src/mcp/install-mcp-server.ts

@@ -35,6 +35,8 @@ export async function prepareMcpConfig(
             REPO_NAME: repo,
             BRANCH_NAME: branch,
             REPO_DIR: process.env.GITHUB_WORKSPACE || process.cwd(),
+            TOKEN_CREATED_AT: new Date().toISOString(),
+            GITHUB_API_URL: process.env.GITHUB_API_URL || "https://api.github.com",
           },
         },
       },