fix: remove SessionStart completion check, keep idle_prompt only

Completion notifications should fire while running (idle), not on restart.

Co-Authored-By: Virgil <virgil@lethean.io>

claude/core/hooks.json

@@ -91,16 +91,6 @@
           }
         ],
         "description": "Restore recent session context on startup"
-      },
-      {
-        "matcher": "*",
-        "hooks": [
-          {
-            "type": "command",
-            "command": "${CLAUDE_PLUGIN_ROOT}/scripts/check-completions.sh"
-          }
-        ],
-        "description": "Report agent completions from previous session"
       }
     ],
     "Notification": [