feat(fleet): provision roster from system-type profile (H3) (#665)

packages/mosaic/src/commands/fleet-personas.ts

@@ -234,6 +234,21 @@ export async function resolvePersona(
     extractClassesFromDir(rolesDir),
     extractClassesFromDir(overrideDir),
   ]);
+  return resolvePersonaFrom(klass, { rolesDir, overrideDir, base, over });
+}
+
+/**
+ * Resolve a single class against ALREADY-EXTRACTED layer maps. Callers that
+ * resolve many classes against the same two directories (e.g. provisioning a
+ * full roster) should {@link extractClassesFromDir} each dir ONCE and reuse the
+ * result here, rather than paying a full directory re-scan per class. Precedence
+ * is identical to {@link resolvePersona}: override layer wins, then baseline.
+ */
+export async function resolvePersonaFrom(
+  klass: string,
+  layers: { rolesDir: string; overrideDir: string; base: DirClasses; over: DirClasses },
+): Promise<PersonaResolution | null> {
+  const { rolesDir, overrideDir, base, over } = layers;
 
   const fromLayer = async (
     dir: string,