feat(gdu): add bundle analyser support for Vite builds

Enable the existing `gdu build -a` / `ANALYZE=true` flag for Vite builds
using rollup-plugin-visualizer. Generates an interactive treemap report at
`bundle-report.html` in the output directory, matching the webpack behaviour.

The plugin is dynamically imported with a try/catch fallback (consistent with
vanilla-extract pattern) so consumers need rollup-plugin-visualizer installed.

AG-17604

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

Author: amir-zahedi

.changeset/vite-bundle-analyser.md

@@ -0,0 +1,5 @@
+---
+"gdu": minor
+---
+
+Add bundle analyser support for Vite builds via `gdu build -a` flag

packages/gdu/commands/build/buildSPA-vite.ts

@@ -96,6 +96,34 @@ export const buildSPAVite = async (guruConfig: GuruConfig) => {
 		}),
 	);
 
+	if (process.env.ANALYZE === 'true') {
+		try {
+			const { visualizer } = await dynamicImport(
+				'rollup-plugin-visualizer',
+			);
+			runtimePlugins.push(
+				visualizer({
+					filename: join(
+						guruConfig.outputPath,
+						'bundle-report.html',
+					),
+					open: false,
+					gzipSize: true,
+					brotliSize: true,
+					template: 'treemap',
+				}),
+			);
+		} catch {
+			console.warn(
+				magenta(
+					'Warning: rollup-plugin-visualizer is not installed. ' +
+						'Install it to enable bundle analysis for Vite builds: ' +
+						'yarn add -D rollup-plugin-visualizer',
+				),
+			);
+		}
+	}
+
 	const { build } = (await dynamicImport('vite')) as {
 		build: (config: InlineConfig) => Promise<unknown>;
 	};