Refuse a placement at the machine's own directories, and use a found directory as found

A module's places setting can move a directory anywhere, and the engine
chowned whatever it was pointed at as root: a directory at /etc owned by the
agent account would hand it /etc (hq ADR 0266). Refuse the machine's roots,
the kernel's and the engine's trees, another account's home, and an archive
or written-into file below an agent's home; and leave the owner and mode of a
directory the mesh did not make.

internal/store/store.go

@@ -131,6 +131,11 @@ type Applied struct {
 	// anything else in the directory, and leaves it in place.
 	Unpacked *Unpacked `json:"unpacked,omitempty"`
 
+	// AsFound is, for a directory, that it was there before the mesh first applied it and was not the
+	// declared owner and mode (novox/hq ADR 0266): the mesh uses it as found, never changing its owner or
+	// mode, and never removes it. Absent on a record from before: such a directory is the mesh's.
+	AsFound bool `json:"as_found,omitempty"`
+
 	// Reads is, for a container, the digest of each file it was created reading — its env-files
 	// and the files mounted into it — by path (novox/hq 04-ISSUES/103).
 	//