refactor(gui): session titles ride the generic projection pair; title-snapshot map retired

The manager's titleSnapshots Map and its session/title frame consumption
dissolve into resident per-session ProjectionValueStores (create-on-demand,
outliving instantiation — the same role the snapshot map played): a
session/projection frame lands whether or not the Session exists, list rows
read the store's 'title' key, subscribed baselines truncate phantom rows, and
session-removed drops the store. The fixture converts to the host parallel:
a projections block on the tail page (title + todos units), push frames on
unit-advancing events, and a post-subscribe projection baseline replacing the
bespoke title control frame.

packages/client/runtime/tests/manager.spec.ts

@@ -133,21 +133,18 @@ describe('list lifecycle', () => {
     expect(manager.getListSnapshot().items.map(i => i.sessionId)).toEqual([S2])
   })
 
-  it('retains monotonic title snapshots before list arrival, merges recency, and clears them on removal', async () => {
+  it('retains title projections before list arrival, keeps last-wins by seq, and clears them on removal', async () => {
     const api = new FakeApiClient()
     const manager = new SessionManager(api)
-    manager.handleMuxEnvelope({
-      rpcId: 'title-new' as never,
-      payload: { type: 'session/title', sessionId: S1, title: 'Newest', eventSeq: 4, updatedAt: 300 },
-    })
-    manager.handleMuxEnvelope({
-      rpcId: 'title-stale' as never,
-      payload: { type: 'session/title', sessionId: S1, title: 'Stale', eventSeq: 3, updatedAt: 900 },
-    })
-    manager.handleMuxEnvelope({
-      rpcId: 'title-equal' as never,
-      payload: { type: 'session/title', sessionId: S1, title: 'Equal', eventSeq: 4, updatedAt: 901 },
-    })
+    const titleFrame = (rpcId: string, title: string, seq: number) => {
+      manager.handleMuxEnvelope({
+        rpcId: rpcId as never,
+        payload: { type: 'session/projection', sessionId: S1, key: 'title', value: title, seq } as never,
+      })
+    }
+    titleFrame('title-new', 'Newest', 4)
+    titleFrame('title-stale', 'Stale', 3)
+    titleFrame('title-equal', 'Equal', 4)
     api.onList = () => Promise.resolve(ok({
       items: [summary(S1), summary(S2, { updatedAt: 200 })] as never[],
     }))
@@ -155,7 +152,7 @@ describe('list lifecycle', () => {
 
     const titled = manager.getListSnapshot()
     expect(titled.items.map(item => item.sessionId)).toEqual([S1, S2])
-    expect(titled.items[0]).toMatchObject({ title: 'Newest', updatedAt: 300 })
+    expect(titled.items[0]?.title).toBe('Newest')
     expect(titled.items[1]?.title).toBeUndefined()
 
     manager.handleHostEnvelope({ rpcId: 'removed' as never, payload: { type: 'host/session-removed', sessionId: S1 } })
@@ -163,34 +160,27 @@ describe('list lifecycle', () => {
     expect(manager.getListSnapshot().items.find(item => item.sessionId === S1)?.title).toBeUndefined()
   })
 
-  it('drops a retained title beyond the subscription baseline before accepting its durable replay', async () => {
+  it('drops a projection row beyond the subscription baseline before accepting its durable replay', async () => {
     const api = new FakeApiClient()
     api.onList = () => Promise.resolve(ok({ items: [summary(S1)] as never[] }))
     const manager = new SessionManager(api)
     await manager.refreshList()
-    manager.handleMuxEnvelope({
-      rpcId: 'title-unflushed' as never,
-      payload: { type: 'session/title', sessionId: S1, title: 'Unflushed', eventSeq: 4, updatedAt: 400 },
-    })
+    const frame = (rpcId: string, payload: object) => {
+      manager.handleMuxEnvelope({ rpcId: rpcId as never, payload: payload as never })
+    }
+    frame('title-unflushed', { type: 'session/projection', sessionId: S1, key: 'title', value: 'Unflushed', seq: 4 })
 
-    manager.handleMuxEnvelope({
-      rpcId: 'subscribed-recovered' as never,
-      payload: { type: 'session/subscribed', sessionId: S1, lastSeq: 2 },
-    })
+    // The durable baseline says the host only knows up to seq 2: the phantom
+    // row rode lost state and must drop, or last-wins pins it forever.
+    frame('subscribed-recovered', { type: 'session/subscribed', sessionId: S1, lastSeq: 2 })
     expect(manager.getListSnapshot().items[0]?.title).toBeUndefined()
-    expect(manager.getListSnapshot().items[0]?.updatedAt).toBe(100)
 
-    manager.handleMuxEnvelope({
-      rpcId: 'title-durable' as never,
-      payload: { type: 'session/title', sessionId: S1, title: 'Durable', eventSeq: 2, updatedAt: 200 },
-    })
-    expect(manager.getListSnapshot().items[0]).toMatchObject({ title: 'Durable', updatedAt: 200 })
+    frame('title-durable', { type: 'session/projection', sessionId: S1, key: 'title', value: 'Durable', seq: 2 })
+    expect(manager.getListSnapshot().items[0]?.title).toBe('Durable')
 
-    manager.handleMuxEnvelope({
-      rpcId: 'subscribed-current' as never,
-      payload: { type: 'session/subscribed', sessionId: S1, lastSeq: 2 },
-    })
-    expect(manager.getListSnapshot().items[0]).toMatchObject({ title: 'Durable', updatedAt: 200 })
+    // A baseline at or past the row's seq keeps it (nothing phantom to drop).
+    frame('subscribed-current', { type: 'session/subscribed', sessionId: S1, lastSeq: 2 })
+    expect(manager.getListSnapshot().items[0]?.title).toBe('Durable')
   })
 })
 

packages/client/runtime/tests/sessions-service.spec.ts

@@ -47,7 +47,7 @@ describe('list store projection', () => {
     const b = bench()
     b.svc.handleMuxEnvelope({
       rpcId: 'title' as never,
-      payload: { type: 'session/title', sessionId: sid('s1'), title: 'Durable title', eventSeq: 2, updatedAt: 3 },
+      payload: { type: 'session/projection', sessionId: sid('s1'), key: 'title', value: 'Durable title', seq: 2 } as never,
     })
     await feedList(b, [
       { id: 's1', cwd: '/home/u/proj-a/' },