feat: Display default model in dropdowns and consolidate Git settings menu (#135)

* types: add commitMessageModel to DesktopSettings

* store: add commitMessageModel state and fetch logic

* lib: implement persistence for commitMessageModel setting

* ui: create GitSettings component for model selection

* ui: add Git section to OpenChamber settings sidebar

* ui: register GitSectionContent in OpenChamberPage

* server: use commitMessageModel setting for AI generation

* tauri: sanitize commitMessageModel in settings commands

* tauri: use commitMessageModel for desktop message generation

* build: update lockfile and package configuration

* refactor(openchamber): improve default model parsing with fallback logic

* feat(openchamber): improve model selection fallback logic

* refactor: move worktree settings into git section

* refactor(openchamber): merge worktree into git section

* refactor[worktree]: simplify empty state layout

* revert: rollback bun.lock and package.json to main

* feat(git): restrict model selection to OpenCode provider

packages/ui/src/lib/desktop.ts

@@ -58,6 +58,7 @@ export type DesktopSettings = {
   defaultAgent?: string;
   autoCreateWorktree?: boolean;
   queueModeEnabled?: boolean;
+  commitMessageModel?: string; // format: "provider/model"
 
   // User-added skills catalogs (persisted to ~/.config/openchamber/settings.json)
   skillCatalogs?: SkillCatalogConfig[];