feat(ext): org collection facet + collection filter in the vault sidebar

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W3b8DA2mXmLWkd4zDbHXHg

extension/src/shared/popup-state.ts

@@ -57,6 +57,7 @@ export interface PopupState {
   orgOffline?: boolean;
   orgConfigs?: OrgConfigSummary[];
   orgCollections?: Collection[];
+  collectionFilter?: string;
   // Vault-tab-only fields. The popup surface leaves these at their defaults
   // (unlocked=false implicit via separate lock-screen view, drawer/panel false).
   // Kept on the shared shape so VaultState satisfies StateHost.getState()