docs: update license from AGPL to PMPL

- Replace AGPL-3.0-or-later with PMPL-1.0-or-later
- Update license name and URLs
- Align with palimpsest-license standard

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: Your Name

README.adoc

@@ -136,7 +136,7 @@ cargo install --path .
 
 == License
 
-Licensed under MIT OR AGPL-3.0-or-later.
+Licensed under MIT OR PMPL-1.0-or-later.
 
 See link:LICENSE.txt[LICENSE.txt] for details.