fix(spec): PROTOCOL_VERSION 13.0.0 → 14.0.0 — re-lockstep with the released package major (#2769)

The #2736 version release bumped @objectstack/spec to 14.0.0 but the
handshake constant was not regenerated, so protocol-version.test.ts fails
on main for every branch (drift guard doing its job).

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: os-zhuang

packages/spec/src/kernel/protocol-version.ts

@@ -15,7 +15,7 @@
  * Kept in lockstep with the package's own major; `protocol-version.test.ts`
  * asserts it against `package.json` so the two cannot drift.
  */
-export const PROTOCOL_VERSION = '13.0.0';
+export const PROTOCOL_VERSION = '14.0.0';
 
 /** The protocol major as an integer — the value the handshake compares. */
 export const PROTOCOL_MAJOR: number = Number.parseInt(PROTOCOL_VERSION.split('.')[0]!, 10);