Keep every composition the engine applied on the machine, so a module whose composition the bus no longer keeps runs as applied and is never composed as nothing (issue 774)

On novox on 2026-10-29 at 07:54 UTC the kept declaration was retired and the node's own composition was in no bucket.
The composer's first pass reads what runs before the agent reads any have (the agent waits for the composer's caught,
sent after that pass), so the node's own was composed with its folded modules running nothing, and the bus server and
four held modules were removed.

- Quick fix: read the node's own have in loadHad too. It still waits for the composer's first pass, and still finds
  nothing when the bucket no longer keeps the composition the have names.
- Thorough fix, chosen: the engine keeps each composition it applied (the node's own too) in `applied/` beside its
  state, 0600. The agent reads it at Run's start, before any watch, as what runs ahead of the bucket and the kept
  declaration. A have naming another running composition wins. An apply keeps; a removal forgets.

Test: a case in TestEverythingIsWhatTheAgentRunsAndWhatIsKeptForTheRest (no new test function). It fails on L3's
engine 4f9227a (0 compositions at the first own composition) and passes here.

cmd/mesh-host/nodeagent.go

@@ -494,7 +494,10 @@ func nodeAgent(ctx context.Context, opts options, signer ed25519.PublicKey, trus
 			// The same kept declaration's filled paths, so a module still running from it keeps its files filled.
 			KeptFilled: func() map[string][]string { _, filled := kept(); return filled },
 			Recorded:   recordedIn(opts.state, say),
-			Inactive:   inactiveIn(&liveness.Exec{Run: apply.ExecRunner, System: builtFor}, heldBy(apply.WindowsIn(filepath.Dir(opts.state)))),
+			// What this engine applied, kept on the machine and read at the start, so what runs is known before the node
+			// composes its own (issue 774).
+			Applied:  appliedStoreFor(opts.state),
+			Inactive: inactiveIn(&liveness.Exec{Run: apply.ExecRunner, System: builtFor}, heldBy(apply.WindowsIn(filepath.Dir(opts.state)))),
 			Revisions: func(ctx context.Context, key string) ([]agent.Update, error) {
 				got, err := session.KVHistory(ctx, composedBucket, key)
 				if err != nil {