Set up GitHub App token for e2e tests (#1)

* feat: Add GitHub App token generator script

Add Python script to generate GitHub App installation tokens from
environment variables (GH_APP_ID and GH_APP_PRIVATE_KEY_PEM_B64).
This is needed to run e2e tests with proper authentication.

* refactor: Convert token generator to uv standalone script

- Add uv inline script metadata with dependencies
- Automatically installs PyJWT, requests, cryptography on uv run
- Update usage documentation to reflect uv usage
- Remove manual dependency installation requirement

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: Phlogistique

get_github_app_token.py

@@ -0,0 +1,93 @@
+#!/usr/bin/env -S uv run
+# /// script
+# requires-python = ">=3.11"
+# dependencies = [
+#     "PyJWT",
+#     "requests",
+#     "cryptography",
+# ]
+# ///
+"""
+GitHub App Token Generator
+
+Generates an installation access token from GitHub App credentials in environment.
+
+Environment variables required:
+- GH_APP_ID: GitHub App ID
+- GH_APP_PRIVATE_KEY_PEM_B64: Base64-encoded private key
+
+Usage:
+    # Run with uv (automatically installs dependencies)
+    uv run get_github_app_token.py
+
+    # Save to file
+    uv run get_github_app_token.py > token.txt
+
+    # Use in shell
+    export GITHUB_TOKEN=$(uv run get_github_app_token.py)
+"""
+
+import base64
+import os
+import sys
+import time
+
+import jwt
+import requests
+
+
+def get_installation_token():
+    """Generate an installation access token for the GitHub App."""
+
+    # Get credentials from environment
+    app_id = os.getenv("GH_APP_ID")
+    private_key_b64 = os.getenv("GH_APP_PRIVATE_KEY_PEM_B64")
+
+    if not all([app_id, private_key_b64]):
+        print("Error: Missing GH_APP_ID or GH_APP_PRIVATE_KEY_PEM_B64", file=sys.stderr)
+        sys.exit(1)
+
+    # Decode private key
+    private_key = base64.b64decode(private_key_b64).decode('utf-8')
+
+    # Generate JWT
+    now = int(time.time())
+    payload = {
+        "iat": now - 60,
+        "exp": now + (10 * 60),
+        "iss": app_id,
+    }
+    jwt_token = jwt.encode(payload, private_key, algorithm="RS256")
+
+    # Get installations
+    headers = {
+        "Authorization": f"Bearer {jwt_token}",
+        "Accept": "application/vnd.github+json",
+        "X-GitHub-Api-Version": "2022-11-28",
+    }
+
+    response = requests.get("https://api.github.com/app/installations", headers=headers)
+    response.raise_for_status()
+    installations = response.json()
+
+    if not installations:
+        print("Error: No installations found for this GitHub App", file=sys.stderr)
+        sys.exit(1)
+
+    # Create installation token
+    installation_id = installations[0]['id']
+    url = f"https://api.github.com/app/installations/{installation_id}/access_tokens"
+    response = requests.post(url, headers=headers)
+    response.raise_for_status()
+
+    token_info = response.json()
+    return token_info['token']
+
+
+if __name__ == "__main__":
+    try:
+        token = get_installation_token()
+        print(token)
+    except Exception as e:
+        print(f"Error: {e}", file=sys.stderr)
+        sys.exit(1)