Take the catalogue's composition rules into the node-engine

ADR 0593 §7: the composer with its refusals leaves mesh-sdk, so mesh-sdk
carries no composition rule. The catalogue functions only the
node-engine's composition reaches (Resolve, Resolution's Compose,
Declaration, DataItems, LeftOut, Rules and the rest, the settings,
placeholder and template refusals, the rendering helpers) are copied
with their tests into internal/compose/resolution; a method of a
mesh-sdk shape becomes a function taking it first. The composition
calls its own copies, and the captured catalogue its tests read lives
here now, shared by mesh-compose's tests.

Claude-Session: https://claude.ai/code/session_01NcbgfJ9Gum47zkFKWRaovL

internal/compose/resolution/laid_values.go

@@ -0,0 +1,38 @@
+package resolution
+
+import (
+	"encoding/json"
+
+	mcat "git.novox.be/novox/mesh-sdk/go/catalogue"
+)
+
+// LaidSource says whether a value resolved from source is laid over a module's files: mesh config, node config and the
+// module's own value are; a manifest's default is not, since it is the composition's already and a taken key is laid
+// only when a layer sets it, never from a default (TakesSettingsField); an unset value is not, since a required one is
+// refused by the composition by name. **The one rule for every composer** (issue 1126, C2): the controller's config
+// read and a node composing its own lay the same values, so the two compose the same files.
+func LaidSource(source string) bool {
+	switch source {
+	case mcat.SourceMesh, mcat.SourceNode, mcat.SourceModule:
+		return true
+	}
+	return false
+}
+
+// LaidValue is one key of mesh-config_resolved read as a composer lays it: its value, and true when its source is laid
+// (LaidSource) and it holds a value; false for a default, an unset value, a source not known and a value that cannot be
+// read.
+func LaidValue(raw []byte) (any, bool) {
+	var r struct {
+		Value  json.RawMessage `json:"value"`
+		Source string          `json:"source"`
+	}
+	if json.Unmarshal(raw, &r) != nil || !LaidSource(r.Source) || len(r.Value) == 0 {
+		return nil, false
+	}
+	var v any
+	if json.Unmarshal(r.Value, &v) != nil {
+		return nil, false
+	}
+	return v, true
+}