refactor: share the live-surface filter between retirement proof preservation and projection

The publication projection already dropped proofs whose surface is live;
reuse that as one helper instead of a second inline scan.

src/main/runtime/mobile-session-terminal-retirement-proof.ts

@@ -1,10 +1,24 @@
 import type {
   RuntimeMobileSessionRetiredTerminalSurface,
+  RuntimeMobileSessionSnapshotTab,
   RuntimeMobileSessionTabsSnapshot
 } from '../../shared/runtime-types'
 
 const MAX_RETIRED_TERMINAL_SURFACE_PROOFS = 64
 
+const surfaceKey = (surface: { parentTabId: string; leafId: string }): string =>
+  `${surface.parentTabId}\0${surface.leafId}`
+
+/** A surface published again is no longer retired, whatever handle now occupies it. */
+export function dropRetirementProofsForLiveSurfaces(
+  retired: readonly RuntimeMobileSessionRetiredTerminalSurface[],
+  tabs: readonly RuntimeMobileSessionSnapshotTab[]
+): RuntimeMobileSessionRetiredTerminalSurface[] {
+  const live = new Set(tabs.flatMap((tab) => (tab.type === 'terminal' ? [surfaceKey(tab)] : [])))
+  return retired.filter((surface) => !live.has(surfaceKey(surface)))
+}
+
+/** Renderer snapshots omit the host's durable close acknowledgements; carry them forward. */
 export function preserveTerminalRetirementProofs(
   snapshot: RuntimeMobileSessionTabsSnapshot,
   existing: RuntimeMobileSessionTabsSnapshot | undefined
@@ -12,22 +26,23 @@ export function preserveTerminalRetirementProofs(
   if (
     !existing?.retiredTerminalSurfaces?.length ||
     existing.worktree !== snapshot.worktree ||
+    // Fence on instance identity only when both sides know it: host-authored snapshots never set it.
     (existing.worktreeInstanceId !== undefined &&
       snapshot.worktreeInstanceId !== undefined &&
       existing.worktreeInstanceId !== snapshot.worktreeInstanceId)
   ) {
     return snapshot
   }
-  const liveSurfaces = new Set(
-    snapshot.tabs.flatMap((tab) =>
-      tab.type === 'terminal' ? [`${tab.parentTabId}\0${tab.leafId}`] : []
+  return {
+    ...snapshot,
+    retiredTerminalSurfaces: dropRetirementProofsForLiveSurfaces(
+      appendRetiredTerminalSurfaceProofs(
+        existing.retiredTerminalSurfaces,
+        snapshot.retiredTerminalSurfaces ?? []
+      ),
+      snapshot.tabs
     )
-  )
-  const retiredTerminalSurfaces = appendRetiredTerminalSurfaceProofs(
-    existing.retiredTerminalSurfaces,
-    snapshot.retiredTerminalSurfaces ?? []
-  ).filter((surface) => !liveSurfaces.has(`${surface.parentTabId}\0${surface.leafId}`))
-  return { ...snapshot, retiredTerminalSurfaces }
+  }
 }
 
 export function appendRetiredTerminalSurfaceProofs(

src/main/runtime/orca-runtime-runtime-id.ts

@@ -103,7 +103,6 @@ export class OrcaRuntimeWithRuntimeId {
     snapshot: RuntimeMobileSessionTabsSnapshot
   ): RuntimeMobileSessionTabsSnapshot {
     const existing = this.mobileSessionTabsByWorktree.get(worktreeId)
-    // Renderer snapshots do not carry the host's durable close acknowledgements.
     snapshot = preserveTerminalRetirementProofs(snapshot, existing)
     const snapshotVersion = existing
       ? Math.max(snapshot.snapshotVersion, existing.snapshotVersion + 1)

src/main/runtime/runtime-mobile-session-result-finalization.ts

@@ -1,4 +1,5 @@
 import type { RuntimeMobileSessionTabsResult } from '../../shared/runtime-types'
+import { dropRetirementProofsForLiveSurfaces } from './mobile-session-terminal-retirement-proof'
 import type {
   RuntimeMobileSessionProjectionHost,
   RuntimeMobileSessionProjectionInput
@@ -41,14 +42,9 @@ export function finalizeRuntimeMobileSessionTabsResult(
     ...(snapshot.tabGroupLayout !== undefined ? { tabGroupLayout } : {}),
     ...(snapshot.retiredTerminalSurfaces
       ? {
-          retiredTerminalSurfaces: snapshot.retiredTerminalSurfaces.filter(
-            (retired) =>
-              !snapshot.tabs.some(
-                (tab) =>
-                  tab.type === 'terminal' &&
-                  tab.parentTabId === retired.parentTabId &&
-                  tab.leafId === retired.leafId
-              )
+          retiredTerminalSurfaces: dropRetirementProofsForLiveSurfaces(
+            snapshot.retiredTerminalSurfaces,
+            snapshot.tabs
           )
         }
       : {}),