feat: add UI customization and model management features (#60)

* feat: add UI customization and model management features

Add comprehensive UI customization options and enhanced model selection:

- **Favorite & Recent Models**: Star models for quick access, track 5 most recent
  - Add favorite/recent sections to model dropdowns
  - Persist preferences in local storage
  - Works in ModelControls and ModelSelector components

- **Tool Call Expansion Settings**: Control default expansion state for tool outputs
  - Three modes: collapsed, activity (summary), detailed
  - Applies to activity groups and individual tool calls
  - Configurable in Appearance Settings

- **Font Size & Spacing Controls**: Adjustable typography and layout density
  - Font size: 50-200% scaling of all semantic typography
  - Spacing/padding: 50-200% scaling of margins, gaps, line heights
  - Real-time preview with reset buttons
  - Settings in Appearance Settings

- **VSCode Extension Settings View**: Full settings access in VSCode extension
  - Add settings navigation and view type
  - Settings button in header
  - Navigate between sessions, chat, and settings

Technical changes:
- Enhanced useUIStore with new state management
- Dynamic CSS variable scaling for typography and spacing
- Typography helper functions for variable access
- ThemeProvider integration for auto-applying scales

* fix: hide theme mode in VSCode and fix detailed tool expansion

- Hide "Theme Mode" setting in VSCode extension settings as VSCode
  dynamically applies its own theme to the extension
- Fix bug where tools from subsequent messages in a turn weren't
  expanded when "Detailed" mode was selected
- Now correctly aggregates all tool IDs from turnGroupingContext when
  calculating effective expanded tools for progressive groups

packages/ui/src/constants/sidebar.ts

@@ -1,4 +1,4 @@
-import { RiBrainAi3Line, RiChatAi3Line, RiCommandLine, RiGitBranchLine, RiPaintBrushLine } from '@remixicon/react';
+import { RiBrainAi3Line, RiChatAi3Line, RiCommandLine, RiGitBranchLine, RiPaintBrushLine, RiStackLine } from '@remixicon/react';
 import type { ComponentType } from 'react';
 
 export type SidebarSection = 'sessions' | 'agents' | 'commands' | 'providers' | 'git-identities' | 'settings';
@@ -32,7 +32,12 @@ export const SIDEBAR_SECTIONS: SidebarSectionConfig[] = [
         description: 'Create and maintain custom slash commands for OpenCode.',
         icon: RiCommandLine,
     },
-
+    {
+        id: 'providers',
+        label: 'Providers',
+        description: 'Configure AI model providers and API credentials.',
+        icon: RiStackLine,
+    },
     {
         id: 'git-identities',
         label: 'Git Identities',