A setting reaches only what declares it, the mesh places its own files, registration refuses a name

Three of novox/hq's group-4 leftovers, one branch.

Issue 173: a module's settings reached every route it contributed, every database it asked for and
every served fact its consumers read — a mail server's site name arrived at the proxy as a route
fact. A setting now overrides a key a contribution or served fact declares and adds none; a file
still merges any key, and a key nothing takes is named as stray instead of dropped silently.

Issue 174: the mesh's own files for a module — its bus credential, its merged config, its bindings —
were placed by the definition under /var/lib/mesh/<module>, 232 host paths in 50 definitions. A
directory may now say `place: "mesh"` and resolves to <root>/mesh/<module>; a directory beneath a
placed one may state its path as `${dir:<id>}/<rest>` and moves with it. The proof test resolves
both catalogues and compares: 48 definitions, no path moved. The controller's own manifest is
converted here; the catalogue in mesh-catalog.

ADR 0155: the installation check moves to registration. `module add` and a build's result both
refuse a definition that names an installation, in the check's words, with the way out; the build
stays recorded.

internal/catalogue/declaration.go

@@ -1161,7 +1161,10 @@ func (r Resolution) contributions(settings SettingsBy, grants []Grant,
 // module wrote another into its configuration.
 func (r Resolution) composed(m Manifest, to string, raw map[string]any, layers []Layer, what string) (
 	map[string]any, error) {
-	values, err := settle(raw, layers, nil, what)
+	// Overridden, not merged: a setting changes a key the contribution declares and adds none.
+	// The provider reads the contribution as a contract, and a setting made for one of this
+	// module's files is no part of it (novox/hq 04-ISSUES/173).
+	values, err := overridden(raw, layers, what)
 	if err != nil {
 		return nil, fmt.Errorf("%s: %w", what, err)
 	}