fix: harden stack validation and lifecycle execution

manage.conf

@@ -1,7 +1,12 @@
 # Maximum number of stacks executed concurrently within each stage.
-# Use 0 for unlimited concurrency.
+# Use 0 for unlimited concurrency. Range: 0-65535; no leading zeros.
 max_parallel 3
 
+# Wait for running/healthy services on up, start, and update.
+# Healthchecks are needed to verify application readiness.
+# Range: 0-86400 seconds; 0 disables waiting. Default: 120 seconds.
+wait_timeout 120
+
 # Each declaration is an ordered stage; stacks on the same line run in parallel.
 # Add --parallel N before the stacks to override max_parallel for that stage.
 # Example: before --parallel 2 stack-a stack-b