149: STRATA_COLD_OVERLAP=4 (zero-copy without the overlap); no residency query for RAM-resident experts

The zero-copy pre-pass ran mincore for every CPU expert of a layer, the RAM copy's too: -2..-9% decode
with an 18 GiB RAM tier. It now skips the RAM-resident and override experts (b32: 0.98/0.97/0.91 ->
1.05/1.10/1.08 vs mode 0, 3 pairs). A file without a residency query (not Linux) never goes zero-copy.

src/core/expert_source.cpp

@@ -1637,6 +1637,9 @@ void FileExpertSource::claim_todo(int64_t layer, const int64_t* experts, int64_t
         for (int64_t i = 0; i < n; ++i) {
             const int64_t e = experts[i];
             if (e < 0 || e >= n_expert_) continue;
+            const size_t index = (size_t) layer * (size_t) n_expert_ + (size_t) e;
+            if (complement_ready_ && resident_blob(index) != nullptr) continue;   // in the RAM copy: no residency query
+            if (!override_.empty() && override_[index] != nullptr) continue;
             uint64_t total = 0;
             const uint64_t c = cached_bytes(layer, e, total, true);
             zc_ok[(size_t) i] = total > 0 && c >= total ? 1 : 0;   // no residency query (not Linux): never