fix(search): make the trimmed-applied-term invariant structural and update the shell contract doc

Review follow-ups on the echo-guard widening:

- setSearchState now trims too, so URL-sourced terms (deep links with
  ?q=Bein%20, actor/discover prefills passing raw provider titles) cannot
  put an untrimmed term into appliedSearchQuery — previously that path
  failed the echo guard's equality check, snapped the box, and dispatched
  the portal search twice. Regression spec added.
- docs/architecture/workspace-shell.md item 8 updated: the applied-term
  echo is now always ignored, not only while input is still debouncing.
- The facade spec's router mock exposes a mutable navigation trigger so
  facade-level tests can exercise the popstate branch.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/architecture/workspace-shell.md

@@ -165,12 +165,18 @@ Search is shell-owned and route-aware:
 8. The URL is authoritative for the search box only when it carries search
    intent. `WorkspaceShellSearchSyncService` re-reads `q` on every
    `NavigationEnd`, but an **app-initiated** navigation that stays on the same
-   page and carries the term already applied is ignored while input is still
-   debouncing — otherwise a page writing an unrelated query param (a downloads
-   filter chip, a refresh bump) or the router echoing back our own `q` would
-   cancel the pending debounce and reset the box, eating everything typed
-   since. Pages are free to write their own query params while the user types;
-   they must not assume the shell will re-apply the search afterwards.
+   page and carries the term already applied is always ignored — whether or
+   not a debounce is still pending. Otherwise a page writing an unrelated
+   query param (a downloads filter chip, a refresh bump) or the router echoing
+   back our own trimmed `q` would reset the box to the applied term, eating
+   everything typed since: the whole word while the first keystroke is still
+   debouncing, or a just-typed trailing space once the debounce has fired
+   ("Bein " would snap to "Bein" and typing on would yield "BeinSports").
+   Applied terms are always stored trimmed (`applySearchQuery` and
+   `setSearchState` both trim), so the echoed `q` compares directly; the box
+   keeps exactly what the user typed. Pages are free to write their own query
+   params while the user types; they must not assume the shell will re-apply
+   the search afterwards.
 9. Browser history overrides that guard. The exemption is keyed on
    `Navigation.trigger === 'imperative'`, so back/forward always re-applies
    what the history entry carries, even mid-typing.

libs/workspace/shell/feature/src/lib/workspace-shell/services/workspace-shell-search-sync.service.spec.ts

@@ -269,6 +269,24 @@ describe('WorkspaceShellSearchSyncService', () => {
         expect(service.appliedSearchQuery()).toBe('Bein');
     });
 
+    it('adopts an externally crafted q with edge whitespace in trimmed form', () => {
+        // A deep link ?q=Bein%20 must not put an untrimmed term into the
+        // applied signal: the URL-sync effect rewrites the URL trimmed, and
+        // an untrimmed applied term would fail the echo guard's equality
+        // check — snapping the box and dispatching the portal search twice.
+        navigateTo(`${DOWNLOADS_URL}?q=Bein%20`);
+
+        expect(service.searchQuery()).toBe('Bein');
+        expect(service.appliedSearchQuery()).toBe('Bein');
+
+        // The trimmed rewrite's echo is our own navigation — skipped.
+        TestBed.flushEffects();
+        navigateTo(`${DOWNLOADS_URL}?q=Bein`);
+
+        expect(service.searchQuery()).toBe('Bein');
+        expect(service.appliedSearchQuery()).toBe('Bein');
+    });
+
     it('syncs the search box from the url when nothing is being typed', () => {
         navigateTo(`${DOWNLOADS_URL}?q=Gamma`);
 

libs/workspace/shell/feature/src/lib/workspace-shell/services/workspace-shell-search-sync.service.ts

@@ -109,10 +109,20 @@ export class WorkspaceShellSearchSyncService {
         this.syncSearchFromUrl(this.routeState.currentUrl());
     }
 
+    /**
+     * Adopts a term from outside the input box (URL `q`, command palette) into
+     * both signals. The trim keeps the applied-terms-are-always-trimmed
+     * invariant structural for URL-sourced values too: an externally crafted
+     * `?q=Bein%20` must not put an untrimmed term into `appliedSearchQuery`,
+     * or the URL-sync effect's trimmed rewrite would fail the echo guard's
+     * equality check and snap the box — the same eaten-keystroke cycle the
+     * guard exists to prevent — while the portal stores dispatch twice.
+     */
     setSearchState(value: string): void {
         this.cancelPendingSearchApply();
-        this.searchQuery.set(value);
-        this.appliedSearchQuery.set(value);
+        const trimmed = value.trim();
+        this.searchQuery.set(trimmed);
+        this.appliedSearchQuery.set(trimmed);
     }
 
     /**

libs/workspace/shell/feature/src/lib/workspace-shell/services/workspace-shell.facade.spec.ts

@@ -117,6 +117,10 @@ describe('WorkspaceShellFacade', () => {
     let playerCommands: {
         ensureEmbeddedMpvSupportLoaded: jest.Mock;
     };
+    // Mirrors Navigation.trigger: 'imperative' is the app navigating,
+    // 'popstate' is the user moving through browser history. Mutable so a
+    // test can exercise the history-authoritative branch of the search sync.
+    let navigationTrigger: 'imperative' | 'popstate';
     let router: {
         url: string;
         events: ReturnType<typeof of>;
@@ -161,6 +165,7 @@ describe('WorkspaceShellFacade', () => {
     };
 
     beforeEach(() => {
+        navigationTrigger = 'imperative';
         showDashboardSignal = signal(true);
         runtime = {
             isElectron: true,
@@ -197,7 +202,7 @@ describe('WorkspaceShellFacade', () => {
             parseUrl: jest.fn((url: string) => createParseUrl(url)),
             createUrlTree: jest.fn(),
             isActive: jest.fn(),
-            lastSuccessfulNavigation: () => ({ trigger: 'imperative' }),
+            lastSuccessfulNavigation: () => ({ trigger: navigationTrigger }),
         };
         playlistsService = {
             clearPortalRecentlyViewed: jest