feat: add microsecond timestamp precision support

google-cloud-bigtable-v2/proto_docs/google/bigtable/v2/data.rb

@@ -651,6 +651,9 @@ class Condition
         #     Deletes cells from the entire row.
         #
         #     Note: The following fields are mutually exclusive: `delete_from_row`, `set_cell`, `add_to_cell`, `merge_to_cell`, `delete_from_column`, `delete_from_family`. If a field in that set is populated, all other fields in the set will automatically be cleared.
+        # @!attribute [rw] timestamp_origin
+        #   @return [::Google::Cloud::Bigtable::V2::Mutation::TimestampOrigin]
+        #     Optional. The origin of the timestamp in this mutation.
         class Mutation
           include ::Google::Protobuf::MessageExts
           extend ::Google::Protobuf::MessageExts::ClassMethods
@@ -760,6 +763,26 @@ class DeleteFromRow
             include ::Google::Protobuf::MessageExts
             extend ::Google::Protobuf::MessageExts::ClassMethods
           end
+
+          # Represents the origin of the timestamp in the mutation.
+          module TimestampOrigin
+            # Default value. Should not be explicitly set.
+            TIMESTAMP_ORIGIN_UNSPECIFIED = 0
+
+            # Indicates that the timestamp was explicitly provided by the user (either
+            # `>0` or `-1` for server-assigned).
+            # The server will reject the mutation if the timestamp's precision does not
+            # match the table's granularity.
+            # (e.g., a millisecond table only allows timestamps that are multiples of
+            # 1000).
+            USER_SPECIFIED = 1
+
+            # Indicates that the timestamp was auto-generated by the client library.
+            # The server will truncate the timestamp's precision to match the table's
+            # granularity.
+            # (e.g., zeroing the last 3 digits for a millisecond table).
+            CLIENT_AUTO_GENERATED = 2
+          end
         end
 
         # Specifies an atomic read/modify/write operation on the latest value of the