fix(memoryFlush): guard transcript-size forced flush against repeated runs (#32358)

The `forceFlushTranscriptBytes` path (introduced in d729ab21) bypasses the
`memoryFlushCompactionCount` guard that prevents repeated flushes within the
same compaction cycle. Once the session transcript exceeds 2 MB, memory flush
fires on every single message — even when token count is well under the
compaction threshold.

Extract `hasAlreadyFlushedForCurrentCompaction()` from the inline guard in
`shouldRunMemoryFlush` and apply it to both the token-based and the
transcript-size trigger paths.

Fixes #32317

Signed-off-by: HCL <chenglunhu@gmail.com>

src/auto-reply/reply/memory-flush.ts

@@ -161,11 +161,22 @@ export function shouldRunMemoryFlush(params: {
     return false;
   }
 
-  const compactionCount = params.entry.compactionCount ?? 0;
-  const lastFlushAt = params.entry.memoryFlushCompactionCount;
-  if (typeof lastFlushAt === "number" && lastFlushAt === compactionCount) {
+  if (hasAlreadyFlushedForCurrentCompaction(params.entry)) {
     return false;
   }
 
   return true;
 }
+
+/**
+ * Returns true when a memory flush has already been performed for the current
+ * compaction cycle. This prevents repeated flush runs within the same cycle —
+ * important for both the token-based and transcript-size–based trigger paths.
+ */
+export function hasAlreadyFlushedForCurrentCompaction(
+  entry: Pick<SessionEntry, "compactionCount" | "memoryFlushCompactionCount">,
+): boolean {
+  const compactionCount = entry.compactionCount ?? 0;
+  const lastFlushAt = entry.memoryFlushCompactionCount;
+  return typeof lastFlushAt === "number" && lastFlushAt === compactionCount;
+}