The mesh's names are written into the hosts file, not over it (hq 128)

/etc/hosts is the machine's: the distribution's localhost lines, the
operator's own entries, and marked blocks other tools maintain there.
Writing node-names whole replaced all of it the moment the private
network was taken, and every later write by those tools was lost at
the next machine joining. The node-names fact is now emitted with
into: "block", so the host owns only its marked region and keeps the
rest byte for byte. The region holds only the mesh's names: no header
claiming the file, no localhost, no 127.0.1.1 line — the floor was
never the mesh's to write. How a fact is written is a property of the
fact in the closed table; node-zones stays a whole file the mesh owns.

Sequencing: a host older than the block mode refuses the whole
declaration on an unknown into, so every host must be upgraded before
this controller is rolled out.

internal/overlay/names.go

@@ -24,9 +24,10 @@ const DefaultSuffix = "internal"
 //
 // This is not the `/etc/hosts` floor the design removes. That floor existed because a node had to
 // reach the mesh's database before its own DNS worked — a fallback for a circularity, and the
-// circularity is gone. This is the mechanism itself: the complete set of names in this mesh,
-// generated whole and owned by the mesh (novox/hq ADR 0011), rather than a patch written
-// underneath something else.
+// circularity is gone. This is the mechanism itself: the complete set of names in this mesh
+// (novox/hq ADR 0011). Written as a marked region *into* the file rather than as the file: the
+// rest of it — `localhost`, the machine's own name, other tools' blocks — is the machine's, and
+// writing it whole replaced all of that (novox/hq issue 128).
 //
 // A file rather than a resolver daemon, deliberately, for now: it works on every Linux, needs no
 // package, and has no failure mode of its own. A daemon becomes necessary when names are wanted