refactor(renderer): keep the fence-reply generation in an import-free module

A dynamic store import inside the refresh was the workaround for the
store -> hydration -> refresh -> store cycle. The counter itself has no
dependencies, so it lives alone and both writers import it statically.

src/renderer/src/lib/legacy-worker-resume-fence-generation.ts

@@ -0,0 +1,12 @@
+// Why a separate module: hydration (inside the store) and the refresh (which writes the store)
+// both bump it; keeping it import-free breaks the store → hydration → refresh → store cycle.
+let generation = 0
+
+/** A newer hydration or request makes every older in-flight fence reply stale. */
+export function advanceLegacyWorkerResumeFenceGeneration(): number {
+  return ++generation
+}
+
+export function currentLegacyWorkerResumeFenceGeneration(): number {
+  return generation
+}

src/renderer/src/lib/legacy-worker-resume-fence-refresh.ts

@@ -1,14 +1,15 @@
-let generation = 0
-export function markLegacyWorkerResumeFencesHydrated(): void {
-  generation++
-}
+import { useAppStore } from '@/store'
+import {
+  advanceLegacyWorkerResumeFenceGeneration,
+  currentLegacyWorkerResumeFenceGeneration
+} from './legacy-worker-resume-fence-generation'
 
 export async function refreshLegacyWorkerResumeFences(): Promise<void> {
-  const requestGeneration = ++generation
+  const requestGeneration = advanceLegacyWorkerResumeFenceGeneration()
   try {
     const fences = await window.api.app.getLegacyWorkerResumeFences()
-    const { useAppStore } = await import('@/store')
-    if (requestGeneration !== generation) {
+    // A reply older than a later request or hydration describes state that has since been replaced.
+    if (requestGeneration !== currentLegacyWorkerResumeFenceGeneration()) {
       return
     }
     useAppStore.setState({ legacyWorkerResumeFencesByPaneKey: fences })

src/renderer/src/store/terminals/workspace-terminal-hydration.ts

@@ -1,4 +1,4 @@
-import { markLegacyWorkerResumeFencesHydrated } from '@/lib/legacy-worker-resume-fence-refresh'
+import { advanceLegacyWorkerResumeFenceGeneration } from '@/lib/legacy-worker-resume-fence-generation'
 import { readWorkspaceSessionResumeFences } from '../../../../shared/workspace-session-resume-fences'
 import type { WorkspaceKey } from '../../../../shared/folder-workspace-types'
 import { FLOATING_TERMINAL_WORKTREE_ID } from '../../../../shared/constants'
@@ -42,7 +42,7 @@ export function createWorkspaceTerminalHydrationActions(
         : null
       const ownershipTransfersByTabId = new Map<string, TerminalLayoutPtyOwnershipTransfer[]>()
       set((s) => {
-        markLegacyWorkerResumeFencesHydrated()
+        advanceLegacyWorkerResumeFenceGeneration()
         const runtimeSessionPlaceholders = buildRuntimeSessionPlaceholders({
           repos: s.repos,
           runtimeHostIdByWorkspaceSessionKey: options?.runtimeHostIdByWorkspaceSessionKey ?? {},