docs(lanes): clarify --no-build is up-only; add A3 spec+plan docs

Help text for "lanes up|down" implied --no-build applied to both;
it's only read by up. Also commits the A3 profile-scaffolding design
spec and implementation plan that weren't yet in git.

bin/ccam.js

@@ -2051,7 +2051,7 @@ const COMMAND_GROUPS = [
       [
         "lanes up|down",
         "[<id>] [--no-build]",
-        "Boot or stop the lane's own app stack (id defaults to the lane owning this directory)",
+        "Boot or stop the lane's own app stack (--no-build: up only; id defaults to the lane owning this directory)",
       ],
       ["lanes runtime", "[<id>]", "Slot, ports, service health and the last boot error"],
       ["lanes logs", "[<id>] <svc> [--tail N]", "Tail one of the lane's hook or service logs"],