feat: V1 prototype — Vite/React/TS tileset generator

- Scaffold: package.json, tsconfig.json, vite.config.ts, index.html
- src/lib/imageProcessor.ts: full pipeline (normalize, offset, seam repair, export, validation)
- src/components/UploadPanel.tsx: drag-and-drop, file picker, clipboard paste
- src/components/SettingsPanel.tsx: all controls per spec
- src/components/PreviewPanel.tsx: Original / Tileable / Repeated tabs
- src/components/ErrorBanner.tsx: dismissible error/warning banners
- src/App.tsx: root component wiring everything together
- src/index.css: dark premium glassmorphism theme w/ Inter font

node_modules/postcss/lib/rule.js

@@ -0,0 +1,27 @@
+'use strict'
+
+let Container = require('./container')
+let list = require('./list')
+
+class Rule extends Container {
+  get selectors() {
+    return list.comma(this.selector)
+  }
+
+  set selectors(values) {
+    let match = this.selector ? this.selector.match(/,\s*/) : null
+    let sep = match ? match[0] : ',' + this.raw('between', 'beforeOpen')
+    this.selector = values.join(sep)
+  }
+
+  constructor(defaults) {
+    super(defaults)
+    this.type = 'rule'
+    if (!this.nodes) this.nodes = []
+  }
+}
+
+module.exports = Rule
+Rule.default = Rule
+
+Container.registerRule(Rule)