fix(apiproxy,client): the list projection column becomes a seedable watermarked block

Review finding (PR #791): the column carried bare values (no seq), so the
client could not seed its value store without risking a stale list block
outranking newer push frames — and nothing consumed the column at all,
leaving cold titles absent after a restart. SessionSummary.projections is
now the same SessionProjectionsBlock as the history tail (values +
asOfSeq; attached rows cut the live registry, cold rows serve the cache's
identity-checked cachedSnapshot whose asOfSeq is the lowest served-row
watermark). SessionManager.refreshList seeds each row's block into the
per-session projection store via per-key apply — partial-baseline
semantics: an absent key never clears, and higher-seq-wins keeps stale
list blocks beneath push frames and tail baselines — so cold titles
surface in the sidebar without opening a session.

packages/client/runtime/src/client/sessions/manager.ts

@@ -212,6 +212,19 @@ export class SessionManager {
             session.handleBlank(s.blank)
             session.handleRunning(s.running)
           }
+          // Seed each row's projection baseline into the per-session value
+          // store (cold titles surface without opening the session). Per-key
+          // apply, not seed(): the list block is a partial baseline — the
+          // cold cache serves only version-matching keys — so an absent key
+          // must not clear; higher-seq-wins still keeps a stale list block
+          // from overwriting a newer push frame or tail baseline.
+          for (const s of result.value.items) {
+            const block = s.projections
+            if (block === undefined) continue
+            const store = this.projectionStore(s.sessionId)
+            const values = block.values as Record<string, unknown>
+            for (const key of Object.keys(values)) store.apply(key, values[key], block.asOfSeq)
+          }
         } else {
           this.listState = 'error'
           this.listError = result.error

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

@@ -160,6 +160,28 @@ describe('list lifecycle', () => {
     expect(manager.getListSnapshot().items.find(item => item.sessionId === S1)?.title).toBeUndefined()
   })
 
+  it('seeds cold titles from the list rows\' projections block under higher-seq-wins', async () => {
+    const api = new FakeApiClient()
+    const manager = new SessionManager(api)
+    // A push frame landed before the list (S2's title is newer than the block's cut).
+    manager.handleMuxEnvelope({
+      rpcId: 'push-newer' as never,
+      payload: { type: 'session/projection', sessionId: S2, key: 'title', value: 'Pushed', seq: 9 } as never,
+    })
+    api.onList = () => Promise.resolve(ok({
+      items: [
+        { ...summary(S1), projections: { asOfSeq: 4, values: { title: 'Cold cached' } } },
+        { ...summary(S2, { updatedAt: 200 }), projections: { asOfSeq: 5, values: { title: 'List stale' } } },
+      ] as never[],
+    }))
+    await manager.refreshList()
+    const items = manager.getListSnapshot().items
+    // Cold row: title surfaces straight from the list block — no open, no history.
+    expect(items.find(item => item.sessionId === S1)?.title).toBe('Cold cached')
+    // The stale list block (seq 5) cannot overwrite the newer push frame (seq 9).
+    expect(items.find(item => item.sessionId === S2)?.title).toBe('Pushed')
+  })
+
   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[] }))