feat: implement game details for launching declared exe and args

[Gustash]

Closes #12

[Copilot]

Pull request overview

This PR implements support for fetching and using game-specific launch details (executable path and arguments) from the IndieGala API. Instead of relying solely on automatic executable detection, the launcher can now use server-provided configuration for Windows games.

Key changes:

• Adds API client functionality to fetch game details including exe path, arguments, and working directory
• Updates launch command to prioritize server-declared executables over local search
• Integrates game details fetching into install and info commands

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
auth/product.go	New file implementing API calls to fetch and cache game launch details (exe path, args, cwd)
launch/launch.go	Adds FindDeclaredExecutable function to retrieve and process server-declared game executables for Windows builds
cmd_launch.go	Updates launch logic to attempt fetching declared executable from server before falling back to local search
cmd_install.go	Adds game details fetching during installation to pre-cache launch information
cmd_info.go	Displays game details (exe path, args, cwd) when showing game information

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.