fix(agent-presets): unify the session event entrypoint and re-address the hermetic skills probe

The persistence catalog recognizes SessionEventMap augmentations of
'@deepseek-ai/dsh-session/types' alone, so the selected event's old
root-specifier declaration compiled but silently vanished from the
generated catalog. The hermetic scaffold e2e still addressed the skill
registry as a preset-realm service; under the layered host registry the
composed agent's view is a scope read, and the ambient-root isolation it
proves is unchanged.

packages/preset/agent-presets/src/session.ts

@@ -15,7 +15,7 @@
 
 import type { SessionEvent, SessionHeader } from '@deepseek-ai/dsh-session'
 
-declare module '@deepseek-ai/dsh-session' {
+declare module '@deepseek-ai/dsh-session/types' {
   interface SessionEventMap {
     /**
      * The session's agent preset was chosen after creation, while the session