feat: Add MongoIdempotencyStoreOptions for MongoDB configuration

feat: Implement BsonJsonConverter for converting BsonDocument and BsonArray to JSON

fix: Update project file to include MongoDB.Bson package

test: Add GraphOverlayExporterTests to validate NDJSON export functionality

refactor: Refactor Program.cs in Attestation Tool for improved argument parsing and error handling

docs: Update README for stella-forensic-verify with usage instructions and exit codes

feat: Enhance HmacVerifier with clock skew and not-after checks

feat: Add MerkleRootVerifier and ChainOfCustodyVerifier for additional verification methods

fix: Update DenoRuntimeShim to correctly handle file paths

feat: Introduce ComposerAutoloadData and related parsing in ComposerLockReader

test: Add tests for Deno runtime execution and verification

test: Enhance PHP package tests to include autoload data verification

test: Add unit tests for HmacVerifier and verification logic

src/Graph/StellaOps.Graph.Indexer/Incremental/MongoIdempotencyStore.cs

@@ -0,0 +1,34 @@
+using MongoDB.Bson;
+using MongoDB.Driver;
+
+namespace StellaOps.Graph.Indexer.Incremental;
+
+public sealed class MongoIdempotencyStore : IIdempotencyStore
+{
+    private readonly IMongoCollection<BsonDocument> _collection;
+
+    public MongoIdempotencyStore(IMongoDatabase database, MongoIdempotencyStoreOptions? options = null)
+    {
+        ArgumentNullException.ThrowIfNull(database);
+        var resolved = options ?? new MongoIdempotencyStoreOptions();
+        _collection = database.GetCollection<BsonDocument>(resolved.CollectionName);
+    }
+
+    public async Task<bool> HasSeenAsync(string sequenceToken, CancellationToken cancellationToken)
+    {
+        cancellationToken.ThrowIfCancellationRequested();
+        var filter = Builders<BsonDocument>.Filter.Eq("sequence_token", sequenceToken);
+        return await _collection.Find(filter).AnyAsync(cancellationToken).ConfigureAwait(false);
+    }
+
+    public async Task MarkSeenAsync(string sequenceToken, CancellationToken cancellationToken)
+    {
+        cancellationToken.ThrowIfCancellationRequested();
+        var filter = Builders<BsonDocument>.Filter.Eq("sequence_token", sequenceToken);
+        var update = Builders<BsonDocument>.Update.Set("sequence_token", sequenceToken)
+            .SetOnInsert("recorded_at", DateTimeOffset.UtcNow.UtcDateTime);
+
+        await _collection.UpdateOneAsync(filter, update, new UpdateOptions { IsUpsert = true }, cancellationToken)
+            .ConfigureAwait(false);
+    }
+}