fix(cli): generate .d.ts declaration file for the public API entry point

Enable tsup dts generation for src/exports.ts so that dist/exports.d.ts
is produced at build time. The binary entry (index) still skips dts.

Work around the `incremental: true` in the base tsconfig that conflicts
with tsup's DTS worker by overriding it to false in the tsup config.

https://claude.ai/code/session_01SExqFNVoBLQCCAbgAY6LXo

Author: claude

packages/cli/tsup.config.ts

@@ -6,7 +6,16 @@ export default defineConfig({
     exports: "src/exports.ts",
   },
   format: ["esm"],
-  dts: false,
+  dts: {
+    // Only emit declaration files for the public API entry point.
+    // The `index` (binary) entry doesn't need them.
+    entry: { exports: "src/exports.ts" },
+    compilerOptions: {
+      // `incremental` is incompatible with tsup's DTS worker when not emitting
+      // to a single file; disable it here.
+      incremental: false,
+    },
+  },
   clean: true,
   bundle: true,
   // External: CommonJS packages that use Node.js built-ins via require()