B5: sample-remove verb — index-only drop, this-bank scope, confirm-on-last-reference

src/bank_book.cpp

@@ -281,6 +281,39 @@ TransferResult BankBook::copySample(const std::string& sampleId,
     return applyDestAdd(to->index, copy, TransferResult::Copied);
 }
 
+// ---------------------------------------------------------------------------
+// Sample removal (index-only) + the last-reference query
+// ---------------------------------------------------------------------------
+
+RemoveResult BankBook::removeSample(const std::string& sampleId,
+                                    const std::string& fromBankId,
+                                    RemoveScope scope) {
+    if (scope == RemoveScope::AllBanks) {
+        // Latent seam: purge the id from every bank that holds it. fromBankId is
+        // ignored (the id is dropped book-wide). Removed iff at least one drop landed.
+        bool any = false;
+        for (auto& b : banks_)
+            if (b.index.remove(sampleId)) any = true;
+        return any ? RemoveResult::Removed : RemoveResult::RejectedSampleAbsent;
+    }
+
+    // ThisBank (default, the only surfaced verb): drop from the one named source bank.
+    Bank* from = bank(fromBankId);
+    if (from == nullptr) return RemoveResult::RejectedUnknownBank;
+    return from->index.remove(sampleId) ? RemoveResult::Removed
+                                        : RemoveResult::RejectedSampleAbsent;
+}
+
+bool BankBook::hashReferencedElsewhere(const std::string& hash,
+                                       const std::string& exceptBankId) const {
+    if (hash.empty()) return false;  // empty hashes never dedup (mirror findByHash)
+    for (const auto& b : banks_) {
+        if (b.id == exceptBankId) continue;         // the removed-from bank is excluded
+        if (b.index.findByHash(hash) != nullptr) return true;
+    }
+    return false;
+}
+
 // ===========================================================================
 // JSON — writer
 // ===========================================================================