fix: pass user data dir to WXT when using dev:watch --new (#403)

The --new flag creates a fresh temp profile directory but WXT's
chromiumProfile was hardcoded to /tmp/browseros-dev, ignoring it.
Pass BROWSEROS_USER_DATA_DIR env var from the Go dev tool and read
it in web-ext.config.ts.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

apps/agent/web-ext.config.ts

@@ -40,7 +40,7 @@ export default defineWebExtConfig({
       '/Applications/BrowserOS.app/Contents/MacOS/BrowserOS',
   },
   chromiumArgs,
-  chromiumProfile: '/tmp/browseros-dev',
+  chromiumProfile: env.BROWSEROS_USER_DATA_DIR || '/tmp/browseros-dev',
   keepProfileChanges: true,
   startUrls: ['chrome://newtab'],
 })

tools/dev/cmd/watch.go

@@ -74,6 +74,7 @@ func runWatch(cmd *cobra.Command, args []string) error {
 	fmt.Println()
 
 	env := proc.BuildEnv(p, "development")
+	env = append(env, fmt.Sprintf("BROWSEROS_USER_DATA_DIR=%s", userDataDir))
 
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()