fix(session-memory): use displaySessionKey instead of event.sessionKey in entry

The resolveDisplaySessionKey function correctly resolved workspace-based
agent IDs (e.g. agent:main:main → agent:navi:main when workspaceDir
matches the navi agent), but the entry template used event.sessionKey
directly, bypassing the resolution.

src/hooks/bundled/session-memory/handler.ts

@@ -366,7 +366,7 @@ const saveSessionToMemory: HookHandler = async (event) => {
       const entryParts = [
         `# Session: ${dateStr} ${timeStr} UTC`,
         "",
-        `- **Session Key**: ${event.sessionKey}`,
+        `- **Session Key**: ${displaySessionKey}`,
         `- **Session ID**: ${sessionId}`,
         `- **Source**: ${source}`,
         "",