feat(nvim): integrate CodeCompanion with LlamaSwap and Copilot

- Remove old code-companion-config.lua file
- Move LLM configuration to llm.lua with LlamaSwap and Copilot integration
- Add copilot-vim plugin to default.nix
- Update which-key bindings to include new CodeCompanion commands
- Configure CodeCompanion with chat, inline, and command strategies using LlamaSwap adapter
- Add memory configuration with default project files
- Update LSP configuration for CodeCompanion markdown rendering

modules/home/programs/terminal/nvim/default.nix

@@ -42,6 +42,7 @@ in
         aerial-nvim # Code Outline
         codecompanion-nvim # CodeCompanion
         comment-nvim # Code Comments
+        copilot-vim # GitHub Copilot
         diffview-nvim # Diff View
         fidget-nvim # Notification Helper
         gitsigns-nvim # Git Blame