Say on every directory how it treats files it does not know, and check it (issue 1024, ADR 0422)

Every directory and archive resource carries `unknown`: move-out for a home folder whose program writes nothing there (the node-engine, delivered in mesh-host #117, moves the rest to ~/.local/state/mesh-moved/<module>/ with a list), module for ~/.ssh and ~/.claude, program elsewhere; `knows` keeps what a program or the operator relies on (powerlevel10k's compiled files, i3's scripts and the asus/g14 drop-ins, dunst's slack rule, betterbird's records, node-env's forge credential, issue 1033). Two shared folders are no longer declared. Each module's README says it. checks/owned holds every manifest to it; checks/sshdir stays while main's merge check runs it (issue 1035). Tests that pin a manifest follow the new key only. Reviewed in three rounds.

modules/showcase/README.md

@@ -0,0 +1,11 @@
+# showcase
+
+The `showcase` module of the mesh catalogue: installs the package `jq`; claims the seat `the-showcase`.
+
+## Files it does not know
+
+Each directory or archive this module declares says how it treats a file it did not write (ADR 0422, ADR 0416).
+
+- `${dir:mesh-state}`: everything in it is the program's; the mesh moves nothing out (ADR 0422 §2).
+- `${dir:state}`: everything in it is the program's; the mesh moves nothing out (ADR 0422 §2).
+- `/opt/showcase`: everything in it is the program's; the mesh moves nothing out (ADR 0422 §2).

modules/showcase/module.json

@@ -101,13 +101,15 @@
       "id": "mesh-state",
       "type": "directory",
       "mode": "0700",
-      "place": "mesh"
+      "place": "mesh",
+      "unknown": "program"
     },
     {
       "id": "state",
       "type": "directory",
       "mode": "0755",
-      "place": "."
+      "place": ".",
+      "unknown": "program"
     },
     {
       "id": "settings",
@@ -120,7 +122,8 @@
       "id": "packed",
       "type": "archive",
       "path": "/opt/showcase",
-      "artifact": "files"
+      "artifact": "files",
+      "unknown": "program"
     },
     {
       "id": "net",