GitHub tools list_user_installations and list_app_installations fail with app installation auth #110

Problem

The list_user_installations and list_app_installations tools fail when using GitHub App installation authentication (the default auth method in scout-agent).

Errors

list_user_installations:

Resource not accessible by integration - https://docs.github.com/rest/apps/installations#list-app-installations-accessible-to-the-user-access-token

list_app_installations:

A JSON web token could not be decoded - https://docs.github.com/rest

Root Cause

These two endpoints require different authentication than what authenticateApp() provides:

When withContext({ appAuth }) is used, the authenticateApp() function exchanges the app JWT for an installation access token. This works for most repository operations, but these two endpoints specifically need different token types.

Suggested Solutions

1. Remove these tools from the default toolset when using app auth, since they're not compatible
2. Add a separate auth path for list_app_installations that uses the raw JWT instead of exchanging it for an installation token
3. Document the limitation so users know these tools require user token auth
4. Throw a more helpful error when these tools are called with incompatible auth (e.g., "This tool requires a user access token and is not compatible with GitHub App authentication")

Reproduction

1. Set up scout-agent with GitHub App auth
2. Call either github_list_user_installations or github_list_app_installations
3. Observe the errors above