feat(workspaces): archive option + archived-workspaces view

Consume the backend's archive contract (feature/archive-workspaces):

- adapter/http: archive(id)/unarchive(id) (PUT/DELETE /workspaces/:id/archive);
  list(archived?) passes the ?archived= query
- logic/view-model: pure applyArchived(list, id, archived)
- store.svelte: setArchived(id, archived) (optimistic + revert-on-error +
  reconciling refresh); archivedList + refreshArchived() for the archived view
- ui/TileActionBar: new Archive action (the right-click→select action bar)
- ui/HomeHeader: new Archived button opens the archived view
- ui/ArchivedWorkspaces (new): modal listing archived workspaces with
  Unarchive + View (navigates to /<id>)
- ui/WorkspacesHome: wire the Archive action + the Archived modal
- .dispatch/wire.reference.md + backend-handoff.md: record the contract delta

1 files changed, 19 insertions, 0 deletions

diff --git a/src/features/workspaces/ui/HomeHeader.svelte b/src/features/workspaces/ui/HomeHeader.svelte
index fb0be0a..9d26306 100644
--- a/src/features/workspaces/ui/HomeHeader.svelte
+++ b/src/features/workspaces/ui/HomeHeader.svelte
@@ -11,6 +11,7 @@
     onCreate,
     onOpenPlugins,
     onSort,
+    onOpenArchived,
   }: {
     /** Tall geometry: the controls collapse to compact icon buttons and the
      * new-workspace popover becomes a bottom sheet. */
@@ -24,6 +25,8 @@
     onCreate: (slug: string) => Promise<CreateResult>;
     onOpenPlugins: () => void;
     onSort: () => void;
+    /** Open the archived-workspaces view. */
+    onOpenArchived: () => void;
   } = $props();
 
   // ── New workspace popover (today's inline form logic, preserved) ──────────
@@ -119,6 +122,22 @@
         </ul>
       </div>
     {/if}
+
+    <!-- Archived workspaces -->
+    <button
+      type="button"
+      class="btn btn-ghost btn-sm"
+      class:btn-circle={compact}
+      aria-label="Archived workspaces"
+      title="View archived workspaces"
+      onclick={onOpenArchived}
+    >
+      {#if compact}
+        <span aria-hidden="true">🗄</span>
+      {:else}
+        Archived
+      {/if}
+    </button>
   </div>
 </header>