chore: add license text for packages with missing licenses

- @bufbuild/protobuf: Apache-2.0 (from upstream LICENSE file)
- buffers: marked as reviewed (no license in npm)
- chainsaw: MIT/X11 (from npm registry)

.licenses/npm/@bufbuild/protobuf.dep.yml

@@ -5,6 +5,21 @@ type: npm
 summary: A complete implementation of Protocol Buffers in TypeScript, suitable for
   web browsers and Node.js.
 homepage:
-license: other
-licenses: []
+license: apache-2.0
+licenses:
+- sources: LICENSE
+  text: |
+    Copyright 2021-2025 Buf Technologies, Inc.
+
+    Licensed under the Apache License, Version 2.0 (the "License");
+    you may not use this file except in compliance with the License.
+    You may obtain a copy of the License at
+
+        http://www.apache.org/licenses/LICENSE-2.0
+
+    Unless required by applicable law or agreed to in writing, software
+    distributed under the License is distributed on an "AS IS" BASIS,
+    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+    See the License for the specific language governing permissions and
+    limitations under the License.
 notices: []