fix(dsh-plugin-browserskill): include the bsk error hint in the thrown message

The daemon's JSON error envelope carries an actionable hint (e.g.
'choose an input, textarea, or contenteditable element from the latest
snapshot'), but the thrown BskError only embedded the message field, so
the model-facing error text never showed the hint. Append it.

packages/dsh-plugin-browserskill/tests/runner.test.ts

@@ -109,6 +109,7 @@ describe("parseBskJson", () => {
         exitCode: 3,
       });
       expect((error as Error).message).toContain("no browser connected");
+      expect((error as Error).message).toContain("hint: open Chrome");
     }
   });