fix(todo-continuation-enforcer): make compaction guard epoch-aware

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/hooks/todo-continuation-enforcer/compaction-guard.ts

@@ -1,8 +1,37 @@
 import { COMPACTION_GUARD_MS } from "./constants"
 import type { SessionState } from "./types"
 
+export function armCompactionGuard(state: SessionState, now: number): number {
+  const nextEpoch = (state.recentCompactionEpoch ?? 0) + 1
+
+  state.recentCompactionAt = now
+  state.recentCompactionEpoch = nextEpoch
+
+  return nextEpoch
+}
+
+export function acknowledgeCompactionGuard(
+  state: SessionState,
+  compactionEpoch: number | undefined
+): boolean {
+  if (compactionEpoch === undefined) {
+    return false
+  }
+
+  if (state.recentCompactionEpoch !== compactionEpoch) {
+    return false
+  }
+
+  state.acknowledgedCompactionEpoch = compactionEpoch
+  return true
+}
+
 export function isCompactionGuardActive(state: SessionState, now: number): boolean {
-  if (!state.recentCompactionAt) {
+  if (state.recentCompactionAt === undefined || state.recentCompactionEpoch === undefined) {
+    return false
+  }
+
+  if (state.acknowledgedCompactionEpoch === state.recentCompactionEpoch) {
     return false
   }