fix(review): embed asymmetry comment, single-lock assign-marker, dedup-collapse test

tests/test_bank_sync.cpp

@@ -160,6 +160,29 @@ static void testFreshInstanceAppliesFirst() {
     CHECK(d.consumedGeneration == 1);
 }
 
+// Re-import / dedup-collapse path: the extension ingests a sample that already exists in
+// the bank (dedup collapse: the bank_generation counter does NOT advance because no new
+// sample was added), but a new assign_request is still written with a HIGHER assign
+// generation (the ingest disambiguator, independent of bank_generation).
+//
+// The consumeDecision must apply the request — its own generation is the "is this new?"
+// discriminator, and it is strictly greater than lastConsumed. bank_generation does not
+// enter consumeDecision at all; this test proves the two counters are fully independent.
+static void testDedupCollapseAssignAppliesWhenBankGenerationUnchanged() {
+    // Simulate: bank_generation is 5 both before and after the dedup ingest (unchanged).
+    // The assign_request generation is 300 (new; lastConsumed was 200 from the prior assign).
+    // The existing sample resolves (it is in the bank — dedup kept it there).
+    const auto d = consumeDecision(makeReq("pool", "existing-sample-id", 300),
+                                   /*lastConsumed*/ 200, /*resolves*/ true,
+                                   /*isFocusedTarget*/ true);
+    CHECK(d.apply);
+    CHECK(d.bankId == "pool");
+    CHECK(d.sampleId == "existing-sample-id");
+    CHECK(d.consumedGeneration == 300);  // marker advanced to the new assign generation
+    // bank_generation (5) is not a parameter here — this test documents its absence from
+    // consumeDecision: only the assign_request's own generation drives the consume decision.
+}
+
 int main() {
     testParseAbsentAndMalformed();
     testParseValid();
@@ -173,6 +196,7 @@ int main() {
     testAppliedWhenNewTargetResolvable();
     testSameIdNewGenerationReapplies();
     testFreshInstanceAppliesFirst();
+    testDedupCollapseAssignAppliesWhenBankGenerationUnchanged();
 
     if (g_fail == 0) std::printf("All tests passed.\n");
     return g_fail ? 1 : 0;