docs(1.1): RAM footprint analysis + release plan

Fleet resident set ~2.57GB across 18 workers; ~1.5GB is the 86MB import
floor paid 18x. Pinned root cause: topology/__init__ eager re-export of
generate drags the full SQLModel ORM (26 tables, ~38MB) into every worker.

deploy/tmpfiles.d/decnet.conf.j2

@@ -0,0 +1,4 @@
+# /run/decnet hosts bus.sock (UDS, 0660, group={{ group }}).
+# tmpfiles.d recreates it on every boot before any decnet-*.service starts,
+# so the bus worker never silently falls back to ~/.decnet/bus.sock.
+d /run/decnet 0755 root {{ group }} -