Implement Unicode text formatter plugin

- Add unicode-maps.ts with BOLD_MAP, ITALIC_MAP, BOLD_ITALIC_MAP from Unicode Sans-Serif ranges
- Add formatter.ts with transformText(text, style) using the maps
- Add commands.ts registering three editorCallback commands (bold, italic, bold-italic)
- Replace sample plugin boilerplate in main.ts with UnicodeFormatterPlugin wired to registerCommands
- Update manifest.json with correct id, name, and description
- Delete unused settings.ts boilerplate

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/unicode-maps.ts

@@ -0,0 +1,26 @@
+function buildMap(
+    upperStart: number,
+    lowerStart: number,
+    digitStart?: number
+): Record<string, string> {
+    const map: Record<string, string> = {};
+    for (let i = 0; i < 26; i++) {
+        map[String.fromCharCode(65 + i)] = String.fromCodePoint(upperStart + i);
+        map[String.fromCharCode(97 + i)] = String.fromCodePoint(lowerStart + i);
+    }
+    if (digitStart !== undefined) {
+        for (let i = 0; i < 10; i++) {
+            map[String.fromCharCode(48 + i)] = String.fromCodePoint(digitStart + i);
+        }
+    }
+    return map;
+}
+
+// Sans-Serif Bold: U+1D5D4–U+1D5ED (upper), U+1D5EE–U+1D607 (lower), U+1D7EC–U+1D7F5 (digits)
+export const BOLD_MAP: Record<string, string> = buildMap(0x1D5D4, 0x1D5EE, 0x1D7EC);
+
+// Sans-Serif Italic: U+1D608–U+1D621 (upper), U+1D622–U+1D63B (lower)
+export const ITALIC_MAP: Record<string, string> = buildMap(0x1D608, 0x1D622);
+
+// Sans-Serif Bold-Italic: U+1D63C–U+1D655 (upper), U+1D656–U+1D66F (lower)
+export const BOLD_ITALIC_MAP: Record<string, string> = buildMap(0x1D63C, 0x1D656);