feat: implement comprehensive text tool (Phase 11)

Add complete text rendering system with the following features:

**Text Tool Core:**
- TextTool class with click-to-place text functionality
- Text cursor and pointer event handling
- Integration with DrawCommand for undo/redo support

**Text Rendering:**
- Multi-line text support with line height control
- Custom letter spacing
- Text alignment (left/center/right)
- Font families: 13 web-safe fonts + 14 popular Google Fonts
- Dynamic Google Font loading via Web Font Loader API
- Font styles (normal/italic) and weights (100-900)

**Text Dialog UI:**
- Full-featured text editor dialog
- Live preview of text with all formatting
- Font family selection (web-safe + Google Fonts)
- Font size (8-500px), style, and weight controls
- Color picker with hex input
- Text alignment options
- Line height slider (0.5-3x)
- Letter spacing slider (-10 to 50px)
- Multi-line text input with textarea

**State Management:**
- text-store with Zustand + persist middleware
- All text settings preserved across sessions
- Dialog state management (open/close)
- Click position tracking

**Integration:**
- Added text tool to tool palette with Type icon
- Registered TextTool in canvas tool system
- Added TextDialog to editor layout
- Full type safety with TypeScript interfaces

**Undoable:**
- Text rendering fully integrated with command pattern
- Each text insertion creates single undo point
- Proper before/after state capture

This completes Phase 11 of the implementation plan, marking
the transition from MVP to a fully-featured image editor.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

types/index.ts

@@ -6,3 +6,4 @@ export * from './filter';
 export * from './selection';
 export * from './transform';
 export * from './shape';
+export * from './text';

types/text.ts

@@ -0,0 +1,40 @@
+export type TextAlign = 'left' | 'center' | 'right';
+export type TextBaseline = 'top' | 'middle' | 'bottom' | 'alphabetic';
+export type FontStyle = 'normal' | 'italic';
+export type FontWeight = 'normal' | 'bold' | '100' | '200' | '300' | '400' | '500' | '600' | '700' | '800' | '900';
+
+export interface TextSettings {
+  text: string;
+  fontFamily: string;
+  fontSize: number;
+  fontStyle: FontStyle;
+  fontWeight: FontWeight;
+  color: string;
+  align: TextAlign;
+  baseline: TextBaseline;
+  lineHeight: number;
+  letterSpacing: number;
+}
+
+export interface TextStore {
+  settings: TextSettings;
+  isDialogOpen: boolean;
+  clickPosition: { x: number; y: number } | null;
+
+  // Setters
+  setText: (text: string) => void;
+  setFontFamily: (fontFamily: string) => void;
+  setFontSize: (fontSize: number) => void;
+  setFontStyle: (fontStyle: FontStyle) => void;
+  setFontWeight: (fontWeight: FontWeight) => void;
+  setColor: (color: string) => void;
+  setAlign: (align: TextAlign) => void;
+  setBaseline: (baseline: TextBaseline) => void;
+  setLineHeight: (lineHeight: number) => void;
+  setLetterSpacing: (letterSpacing: number) => void;
+  updateSettings: (settings: Partial<TextSettings>) => void;
+
+  // Dialog control
+  openDialog: (x: number, y: number) => void;
+  closeDialog: () => void;
+}