feat: wire cookie-import-browser into browse server

Add cookie-picker route dispatch (no auth, localhost-only), add
cookie-import-browser to WRITE_COMMANDS and CHAIN_WRITE, add serverPort
property to BrowserManager, add write command with two modes (picker UI
vs --domain direct import), update CLI help text.

browse/src/browser-manager.ts

@@ -27,6 +27,9 @@ export class BrowserManager {
   private extraHeaders: Record<string, string> = {};
   private customUserAgent: string | null = null;
 
+  /** Server port — set after server starts, used by cookie-import-browser command */
+  public serverPort: number = 0;
+
   // ─── Ref Map (snapshot → @e1, @e2, @c1, @c2, ...) ────────
   private refMap: Map<string, Locator> = new Map();