docs: add noncommercial license

- Add the PolyForm Noncommercial License 1.0.0 with the required copyright notice.
- Declare the license file in Python package metadata.
- Document that commercial use is not permitted without separate licensing.
- Refresh the extension packaging wording to match the testing archive name.

README.md

@@ -491,7 +491,7 @@ The extension source lives in `extension/src/`. `extension/background.js` and `e
 Packaging:
 
 ```bash
-npm run package:extension           # local/unpacked zip, keeps manifest.key for stable native-messaging ID
+npm run package:extension           # testing/unpacked zip, keeps manifest.key for stable native-messaging ID
 npm run package:extension:webstore  # Chrome Web Store zip, strips manifest.key
 ```
 
@@ -505,3 +505,11 @@ Chrome Web Store rejects `manifest.key`, so upload the `*-webstore-*` zip from `
 - **Multiple browser instances can be auto-distinguished, but generated aliases are temporary**. Unaliased browsers get UUID aliases from the native host, which avoids collisions but is less ergonomic than setting a stable alias with `browser-cli clients rename --browser <current-alias> <new-alias>`.
 - **Supported install targets are explicit, not “all Chromium browsers”**. The installer currently supports Chrome, Chromium, Brave, Edge, and Vivaldi. Other Chromium-based browsers may use different or shared native messaging manifest locations, so they need browser-specific verification before being added safely.
 - **Linux and macOS only** — Windows native messaging paths are not yet handled.
+
+---
+
+## License
+
+PolyForm Noncommercial License 1.0.0. See [LICENSE](LICENSE).
+
+Commercial use is not permitted under this license. For commercial licensing, contact the project maintainer.