feat(client-runtime): project the archive set and the archiveSession action

WorkspaceListState gains archivedSessionIds (ReadonlySet, replaced only
on membership change), installed as full snapshots from the list
baseline, the unary echo, and the changed frame. Archiving the current
session clears the selection into the New Session view state. Test
doubles (test-runtime, fake APIs, fixture client) follow the widened
IWorkspaces/IApiClient faces.

packages/client/ui-conversation/tests/chat-code-subcalls.spec.tsx

@@ -128,7 +128,7 @@ async function bench(snapshot: ConversationSnapshot) {
   ctx.provide('sessions', sessionsFake)
   const workspaces = {
     list: createSnapshotStore<WorkspaceListState>({
-      items: [], state: 'idle', phase: 'ready', error: null,
+      items: [], archivedSessionIds: new Set(), state: 'idle', phase: 'ready', error: null,
       baselinesReady: true, recentWorkspaceId: undefined,
     }),
     startSession: vi.fn(),

packages/client/ui-conversation/tests/chat-view.spec.tsx

@@ -94,7 +94,7 @@ function emptySessions() {
 
 function emptyWorkspaces() {
   const store = createSnapshotStore<WorkspaceListState>({
-    items: [], state: 'idle', phase: 'ready', error: null,
+    items: [], archivedSessionIds: new Set(), state: 'idle', phase: 'ready', error: null,
     baselinesReady: true, recentWorkspaceId: undefined,
   })
   return bindSnapshotSelector(store)

packages/client/ui-conversation/tests/gate-branch-tails.spec.tsx

@@ -74,7 +74,7 @@ describe('render branch tails', () => {
     const emptyList = createSnapshotStore<SessionListState>(
       { ids: [], byId: {}, current: undefined, phase: 'ready' })
     const emptyWorkspaces = createSnapshotStore<WorkspaceListState>({
-      items: [], state: 'idle', phase: 'ready', error: null,
+      items: [], archivedSessionIds: new Set(), state: 'idle', phase: 'ready', error: null,
       baselinesReady: true, recentWorkspaceId: undefined,
     })
     const view = render(
@@ -111,7 +111,7 @@ describe('render branch tails', () => {
     const emptyList = createSnapshotStore<SessionListState>(
       { ids: [], byId: {}, current: undefined, phase: 'ready' })
     const emptyWorkspaces = createSnapshotStore<WorkspaceListState>({
-      items: [], state: 'idle', phase: 'ready', error: null,
+      items: [], archivedSessionIds: new Set(), state: 'idle', phase: 'ready', error: null,
       baselinesReady: true, recentWorkspaceId: undefined,
     })
     const view = render(

packages/client/ui-conversation/tests/input-bar.spec.tsx

@@ -96,7 +96,7 @@ function bench(over?: BenchOptions) {
       ids: [], byId: {}, current: undefined, phase: 'ready',
     })),
     useWorkspaces: bindSnapshotSelector(createSnapshotStore({
-      items: [], state: 'idle', phase: 'ready', error: null,
+      items: [], archivedSessionIds: new Set(), state: 'idle', phase: 'ready', error: null,
       baselinesReady: true, recentWorkspaceId: undefined,
     })),
     useProjection: ((key: string, selector?: (v: unknown) => unknown) =>

packages/client/ui-conversation/tests/input-matrix.spec.tsx

@@ -39,7 +39,7 @@ function mountBar(shell: SessionInputShell, over?: { running?: boolean; disabled
       ids: [], byId: {}, current: undefined, phase: 'ready',
     })),
     useWorkspaces: bindSnapshotSelector(createSnapshotStore({
-      items: [], state: 'idle', phase: 'ready', error: null,
+      items: [], archivedSessionIds: new Set(), state: 'idle', phase: 'ready', error: null,
       baselinesReady: true, recentWorkspaceId: undefined,
     })),
     useProjection: (() => undefined),

packages/client/ui-conversation/tests/input-scenarios.spec.tsx

@@ -125,7 +125,7 @@ async function scopedBench(register?: (slash: SlashService) => void) {
       ids: [], byId: {}, current: undefined, phase: 'ready',
     })),
     useWorkspaces: bindSnapshotSelector(createSnapshotStore({
-      items: [], state: 'idle', phase: 'ready', error: null,
+      items: [], archivedSessionIds: new Set(), state: 'idle', phase: 'ready', error: null,
       baselinesReady: true, recentWorkspaceId: undefined,
     })),
     useProjection: (() => undefined),

packages/client/ui-conversation/tests/skeleton.spec.tsx

@@ -62,7 +62,7 @@ function workspace(id = 'w1'): WorkspaceView {
 }
 
 const workspaceState = (items: readonly WorkspaceView[]): WorkspaceListState => ({
-  items, state: 'idle', phase: 'ready', error: null,
+  items, archivedSessionIds: new Set(), state: 'idle', phase: 'ready', error: null,
   baselinesReady: true, recentWorkspaceId: undefined,
 })
 

packages/client/ui-conversation/tests/terminal-card.spec.tsx

@@ -429,7 +429,7 @@ describe('DetailsPanel Output section', () => {
         phase: 'ready',
       })
     const workspaces = createSnapshotStore<WorkspaceListState>({
-      items: [], state: 'idle', phase: 'ready', error: null,
+      items: [], archivedSessionIds: new Set(), state: 'idle', phase: 'ready', error: null,
       baselinesReady: true, recentWorkspaceId: undefined,
     })
     return render(
@@ -607,7 +607,7 @@ describe('DetailsPanel Output section', () => {
         useSessions={bindSnapshotSelector(createSnapshotStore<SessionListState>(
           { ids: [], byId: {}, current: undefined, phase: 'ready' }))}
         useWorkspaces={bindSnapshotSelector(createSnapshotStore<WorkspaceListState>({
-          items: [], state: 'idle', phase: 'ready', error: null,
+          items: [], archivedSessionIds: new Set(), state: 'idle', phase: 'ready', error: null,
           baselinesReady: true, recentWorkspaceId: undefined,
         }))}
         useInput={(() => { throw new Error('unused') })}