issue 1840/S6: keep the node's packages in installed, read at the keeper's start and at every released lock

The keeper reads pacman's database into installed.<node> and writes it only when it differs from the key,
says each change as package.changed, and keeps the last value when the list is over the bus's cap, marking
the node not current until it fits again; the health names the size. The loop runs over injected states,
events, clock, watch and machine, and leaves hooks (start, after a transaction, state watches, wakes) for the
upgrade parts of ADR 0508.

modules/pacman/go.mod

@@ -3,3 +3,12 @@ module pacman
 go 1.26.0
 
 require git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261022121659-076e1f7947db
+
+require (
+	github.com/klauspost/compress v1.20.0 // indirect
+	github.com/nats-io/nats.go v1.54.0 // indirect
+	github.com/nats-io/nkeys v0.4.16 // indirect
+	github.com/nats-io/nuid v1.0.1 // indirect
+	golang.org/x/crypto v0.57.0 // indirect
+	golang.org/x/sys v0.48.0
+)