fix(github): send User-Agent on all GitHub API calls (#400)

Cloudflare Workers' fetch doesn't set a default User-Agent, and
GitHub's API rejects UA-less requests with 403 "Request forbidden
by administrative rules" — the worker was crashing at upstream tool
discovery (getAppInstallationToken) on the very first request.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: viktormarinho

github/server/lib/github-app-auth.ts

@@ -154,6 +154,7 @@ export async function getAppInstallationToken(): Promise<string> {
         Authorization: `Bearer ${jwt}`,
         Accept: "application/vnd.github+json",
         "X-GitHub-Api-Version": "2022-11-28",
+        "User-Agent": "deco-cms-github-mcp",
       },
     },
   );
@@ -186,6 +187,7 @@ export async function getAppInstallationToken(): Promise<string> {
         Authorization: `Bearer ${jwt}`,
         Accept: "application/vnd.github+json",
         "X-GitHub-Api-Version": "2022-11-28",
+        "User-Agent": "deco-cms-github-mcp",
       },
     },
   );

github/server/lib/github-client.ts

@@ -26,6 +26,7 @@ async function postToGitHub(
     headers: {
       Accept: "application/json",
       "Content-Type": "application/json",
+      "User-Agent": "deco-cms-github-mcp",
     },
     body: JSON.stringify(body),
   });

github/server/lib/installation-map.ts

@@ -124,6 +124,7 @@ export async function captureInstallationMappings(
             Authorization: `Bearer ${token}`,
             Accept: "application/vnd.github+json",
             "X-GitHub-Api-Version": "2022-11-28",
+            "User-Agent": "deco-cms-github-mcp",
           },
         },
       );

github/server/lib/mcp-proxy.ts

@@ -29,6 +29,7 @@ function connectUpstreamClient(token: string): Promise<Client> {
       requestInit: {
         headers: {
           Authorization: `Bearer ${token}`,
+          "User-Agent": "deco-cms-github-mcp",
         },
       },
     },