feat(m4b): add vault selection UI, enable/disable toggle, missing-installed UI

- Add VaultSelection.svelte: first-run vault create/open/recent UI
- Update App.svelte: vault check on startup, show VaultSelection when needed
- Update PluginCard.svelte: enable/disable buttons, vault state awareness
- Update PluginManager.svelte: enable/disable handlers, missing-installed section
- Add SetCurrentVault Wails API binding
- Add RecordDesiredPlugin Wails API binding
- Record desired plugins on discovery (only when vault open)
- Fix addRecent: remove duplicate sort, clean up unused import
- Update smoke-platform.sh: enable/disable lifecycle test
- Add runEnableDisableTest: vault create/open, disable/enable, plugins.json verify

scripts/smoke-platform.sh

@@ -63,5 +63,15 @@ if [ "$SMOKE_EXIT" -ne 0 ]; then
   exit 1
 fi
 
+# ── test enable/disable via Go smoke ──
+echo ""
+echo "[go smoke: enable/disable]"
+(cd "$ROOT" && go run -mod=mod ./cmd/smoke-platform/ -test-enable-disable 2>&1)
+SMOKE_ED_EXIT=$?
+if [ "$SMOKE_ED_EXIT" -ne 0 ]; then
+  echo "  ❌ smoke-platform: enable/disable test failed"
+  exit 1
+fi
+
 echo ""
 echo "✅ smoke-platform done"