refactor: Cleanup git state - commit all staged changes

Major refactoring cleanup:
- Add new controller architecture (class-controller-*.php)
- Add new settings-v2 UI (views/settings-v2/)
- Add new CSS architecture (agentic-sidebar.css, tokens)
- Add esbuild build pipeline (scripts/build.js, package.json)
- Add composer dependencies (vendor/)
- Add frontend src directory (assets/js/src/index.jsx)
- Add documentation files
- Remove old/obsolete files (class-settings.php, old CSS)

This commits all pending changes from previous refactoring efforts.

scripts/build.js

@@ -0,0 +1,77 @@
+/**
+ * Build script for WP Agentic Writer sidebar
+ * Compiles index.jsx to dist/sidebar.js
+ */
+
+const esbuild = require("esbuild");
+const path = require("path");
+const fs = require("fs");
+
+const srcPath = path.join(__dirname, "..", "assets", "js", "src", "index.jsx");
+const distPath = path.join(
+  __dirname,
+  "..",
+  "assets",
+  "js",
+  "dist",
+  "sidebar.js",
+);
+
+// Ensure dist directory exists
+const distDir = path.dirname(distPath);
+if (!fs.existsSync(distDir)) {
+  fs.mkdirSync(distDir, { recursive: true });
+}
+
+const isWatch = process.argv.includes("--watch");
+
+const buildOptions = {
+  entryPoints: [srcPath],
+  bundle: true,
+  outfile: distPath,
+  // The source file is already a self-invoking IIFE: (function(wp){...})(window.wp).
+  // Use anonymous IIFE wrapping WITHOUT a globalName so we never assign to (and
+  // thereby clobber) the global `wp` that WordPress provides.
+  format: "iife",
+  target: ["es2019"],
+  minify: !isWatch,
+  sourcemap: isWatch,
+
+  // JSX settings - WordPress uses createElement
+  jsx: "transform",
+  jsxFactory: "wp.element.createElement",
+  jsxFragment: "wp.element.Fragment",
+
+  // WordPress globals
+  define: {
+    "process.env.NODE_ENV": isWatch ? '"development"' : '"production"',
+  },
+
+  // External dependencies (loaded by WordPress)
+  external: [],
+
+  logLevel: "info",
+};
+
+async function build() {
+  if (isWatch) {
+    const ctx = await esbuild.context(buildOptions);
+    await ctx.watch();
+    console.log("👀 Watching for changes...");
+
+    // Handle cleanup on exit
+    process.on("SIGINT", async () => {
+      console.log("\n✖ Stopping watcher...");
+      await ctx.dispose();
+      process.exit(0);
+    });
+  } else {
+    const result = await esbuild.build(buildOptions);
+    console.log("✅ Build complete!");
+  }
+}
+
+build().catch((err) => {
+  console.error("❌ Build failed:", err);
+  process.exit(1);
+});