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/betterbird/module.json

@@ -83,7 +83,9 @@
       "type": "directory",
       "path": "${machine:account-home}/.config/betterbird",
       "owner": "${machine:account}",
-      "mode": "0755"
+      "mode": "0755",
+      "unknown": "move-out",
+      "knows": ["accounts-record.json", "configuration-record.json", "kept/"]
     },
     {
       "id": "prefs",
@@ -150,31 +152,36 @@
       "id": "installation",
       "type": "archive",
       "path": "/opt/betterbird",
-      "artifact": "archive"
+      "artifact": "archive",
+      "unknown": "program"
     },
     {
       "id": "owl",
       "type": "archive",
       "path": "/opt/betterbird/owl",
-      "artifact": "owl"
+      "artifact": "owl",
+      "unknown": "program"
     },
     {
       "id": "policies",
       "type": "archive",
       "path": "/opt/betterbird/distribution",
-      "artifact": "distribution"
+      "artifact": "distribution",
+      "unknown": "program"
     },
     {
       "id": "spelling",
       "type": "archive",
       "path": "/opt/betterbird/defaults/pref",
-      "artifact": "defaults"
+      "artifact": "defaults",
+      "unknown": "program"
     },
     {
       "id": "preparation",
       "type": "archive",
       "path": "/usr/local/lib/mesh-betterbird",
-      "artifact": "tools"
+      "artifact": "tools",
+      "unknown": "program"
     },
     {
       "id": "start",