Give a service's held state its own field and key, so main compiles again

#64/#65 and #66 each added Applied.Declared: a directory's declared owner and
mode (string) and a service's held state (*FoundUnit), both under the JSON key
"declared". The directory's is already on nodes, written by d28ca95, so it
keeps the name and key; the service's becomes DeclaredUnit, "declared_unit".
#66 never deployed, so no node holds a record under the new key.

internal/store/store.go

@@ -99,12 +99,13 @@ type Applied struct {
 	// when its declaration goes; one the mesh started is stopped again. Absent on a record written
 	// before the host kept it, and then the unit is left exactly as it is.
 	Found *FoundUnit `json:"found,omitempty"`
-	// Declared is, for a service with a state, what the mesh last held its unit to: running or stopped,
+	// DeclaredUnit is, for a service with a state, what the mesh last held its unit to: running or stopped,
 	// and enabled or disabled where the declaration said. With Found, it tells a unit the mesh's own
 	// declaration stopped and disabled from one somebody stopped since, so removal gives back running
 	// and enabled only the first (novox/hq ADR 0269). Absent on a record from before the host kept it,
 	// and then nothing is started on the way out.
-	Declared *FoundUnit `json:"declared,omitempty"`
+	// Its key is not "declared": that one is a directory's (AsFound, below) and was on disk first.
+	DeclaredUnit *FoundUnit `json:"declared_unit,omitempty"`
 
 	// Into is set for a file written into rather than over (novox/hq ADR 0102): the format, what
 	// each of the mesh's keys held before it set them, which of them were absent, and whether the