feat(dashboard): capabilities helper for role-aware UI shadowing

Pure-function module that mirrors crates/manager-core/src/authz.rs and
lets dashboard pages decide which create / edit / delete affordances to
render. Widens the vitest include so the truth-table test runs.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

dashboard/src/lib/capabilities.ts

@@ -0,0 +1,43 @@
+// Permission predicates the dashboard uses to shadow create / edit /
+// delete affordances. Mirrors the canonical role → capability rules in
+// crates/manager-core/src/authz.rs:
+//
+//   owner / admin instance role → implicit app_admin on every app
+//   app_admin                   → settings, domain claims, delete app, delete scripts
+//   editor                      → CRUD on scripts, routes, sandbox config (no script delete)
+//   viewer                      → read scripts + execution logs
+//   member with no membership   → no access
+//
+// These helpers are read-only and have no Svelte runes — callers pass
+// the current `MeDto` and (when relevant) the per-app `my_role` they
+// already hold. Hiding here never authorizes anything; the backend's
+// `require(Capability::…)` is always the ground truth.
+
+import type { AppRole, MeDto } from './api';
+
+/** Owner + admin only. Members never see "New app". */
+export function canCreateApp(me: MeDto | null): boolean {
+	if (!me) return false;
+	return me.instance_role === 'owner' || me.instance_role === 'admin';
+}
+
+/** Owner + admin only — the "Users" admin page is also gated this way. */
+export function canManageUsers(me: MeDto | null): boolean {
+	if (!me) return false;
+	return me.instance_role === 'owner' || me.instance_role === 'admin';
+}
+
+/** Can mutate scripts and routes (Save, +Add route, remove route). */
+export function canWriteApp(me: MeDto | null, appMyRole: AppRole | null): boolean {
+	if (!me) return false;
+	if (me.instance_role === 'owner' || me.instance_role === 'admin') return true;
+	return appMyRole === 'app_admin' || appMyRole === 'editor';
+}
+
+/** Can take app-admin actions: app settings, domain claims, delete
+ *  app, delete scripts, manage members. */
+export function canAdminApp(me: MeDto | null, appMyRole: AppRole | null): boolean {
+	if (!me) return false;
+	if (me.instance_role === 'owner' || me.instance_role === 'admin') return true;
+	return appMyRole === 'app_admin';
+}