refactor implementation to use more ghostty (#12)

* Phase 2: Replace TypeScript VT parser/buffer with WASM terminal

- Added GhosttyTerminal class (311 lines) wrapping WASM terminal emulator
- Created TerminalAdapter to bridge WASM cells to renderer format
- Updated Terminal class to use WASM backend instead of ScreenBuffer + VTParser
- Made CanvasRenderer duck-typed with IRenderable interface
- Deleted lib/buffer.ts (840 lines) and lib/vt-parser.ts (635 lines)
- Created lib/buffer-types.ts (29 lines) for minimal type compatibility
- Updated WASM binary to 404 KB (includes terminal exports)
- All 86 tests passing
- Net: -1,475 lines (-33% codebase reduction)

Benefits:
- Production-tested VT100 emulation from Ghostty
- Simplified codebase (1,475 fewer lines to maintain)
- Maintained xterm.js-compatible API
- All existing tests pass without modification
* Update WASM binary with width bug fix
- Cells now have correct width values (1 for normal, 2 for wide, 0 for spacers)
- Fixes rendering issue where characters were not visible
- Updated from phase1 commit 811a60d60

Author: sreya

bun.lock

@@ -0,0 +1,28 @@
+/**
+ * Buffer type definitions
+ * 
+ * These types are used by the renderer for backward compatibility.
+ * The actual terminal buffer is now implemented in WASM (GhosttyTerminal).
+ */
+
+/** Color types for rendering */
+export type CellColor = 
+  | { type: 'default' }
+  | { type: 'palette'; index: number }
+  | { type: 'rgb'; r: number; g: number; b: number };
+
+/** Cell represents a single character position for rendering */
+export interface Cell {
+  char: string;              // The character (may be multi-byte UTF-8)
+  width: number;             // 1 for normal, 2 for wide (CJK/emoji), 0 for combining
+  fg: CellColor;
+  bg: CellColor;
+  bold: boolean;
+  italic: boolean;
+  underline: boolean;
+  inverse: boolean;
+  invisible: boolean;
+  strikethrough: boolean;
+  faint: boolean;
+  blink: boolean;
+}