seed: carry restart approval policy into new worlds

Make legacy core.exit share core.restart's supervisor gate and pending
request. Seed the stable agent prompt and boot comments with the approval
and shutdown contract, and check real init output under a deadline.
Cover both aliases' gate, response grace, coalescing and exit status.

Card: SAU-135

cli/src/boot.yaml

@@ -2,6 +2,9 @@
 # Each method is a plugin.method name. params contains its named arguments.
 # The core waits for each result before it starts the next service.
 # After a plugin upgrade, the core restarts that plugin's services.
+# Host restart is separate: #loop sets SAUSAGE_LOOP=1 to enable core.restart
+# (and its alias core.exit). It answers before clean shutdown with exit code 75.
+# Agents need the person's explicit approval each time; never add it as a service.
 # Example (replace [] with this list):
 # - method: www.start
 #   params: