Merge main, and close what the confirmation review found (hq ADR 0272)

- Any failure of a request the link may have delivered now says the line
  may have run; "nothing ran" is said only of a request the link knows it
  never asked (no link open, nobody listening: link.ErrNotAsked).
- A test holds that a connection saying nothing is answered within its
  deadline, set at accept, and gives its slot back.
- The README says the socket refuses a process outside the machine's own
  namespaces, so flatpak, toolbox and distrobox shells are refused.

README.md

@@ -151,6 +151,19 @@ carries. The claim is not. The foundation is four container services, and:
 So `foundation.lock` here is a real bundle with a placeholder's content. Saying that plainly
 beats shipping a host that claims a foundation it has never raised.
 
+## mesh-cli's socket (novox/hq ADR 0272)
+
+The engine serves `/run/nox-mesh-host/cli.sock` for `mesh-cli`, the operator's command (`internal/meshcli`). It
+reads the asking account from the kernel (`SO_PEERCRED`) and asks the controller on this node's own subject; the
+controller decides what the line may do, and the engine runs nothing it receives. One line per connection, each
+connection's deadline set the moment it is accepted, two lines at once per account and eight for the machine,
+"busy" beyond that.
+
+**A process outside the machine's own namespaces is refused**, whatever its user id: the peer's mount and user
+namespace must be the engine's. So `mesh-cli` run inside a flatpak, a toolbox or distrobox container, or any other
+container — even one running as the operator's own id — is refused with the reason; run it from the machine's own
+shell.
+
 ## A capability is detected, never assumed
 
 The reason this is the first thing built rather than a detail of it.