r105 v0.3.1

Beyond the prompt. Cleaned up references to llama-router (private internal tool). r105 now stands on its own as a backend-agnostic terminal AI assistant.

Changelog

• Removed llama-router mentions and dead link from README, CONTRIBUTING.md
• Fixed PyPI description to be backend-agnostic
• Version bumped to 0.3.1
• Updated Homebrew/Scoop formulas