POC: extension entry + esbuild bundle (Feature #2)

activate() registers showClineSdkInfo, which renders the SDK summary to a
notification and output channel. esbuild bundles to CJS, keeping vscode and
@cline/sdk external (the ESM SDK loads via runtime dynamic import).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

esbuild.mjs

@@ -0,0 +1,27 @@
+import { build, context } from "esbuild";
+
+const watch = process.argv.includes("--watch");
+
+/** @type {import('esbuild').BuildOptions} */
+const options = {
+  entryPoints: ["src/extension.ts"],
+  outfile: "out/extension.cjs",
+  bundle: true,
+  platform: "node",
+  format: "cjs",
+  target: "node20",
+  sourcemap: true,
+  // vscode is provided by the host; @cline/sdk is ESM-only and is loaded at
+  // runtime via dynamic import() from node_modules, so keep both external.
+  external: ["vscode", "@cline/sdk"],
+  logLevel: "info",
+};
+
+if (watch) {
+  const ctx = await context(options);
+  await ctx.watch();
+  console.log("esbuild: watching…");
+} else {
+  await build(options);
+  console.log("esbuild: build complete → out/extension.cjs");
+}