📚 Add missing changelog entry and document changelog locations

Add changelog entry for the fix-incorrect-invitation-token-handling
change (PR #9380) under `## 2.15.0 (Unreleased)` > `🐛 Bugs fixed`.
Add a `## Changelogs` section to AGENTS.md documenting both changelog
locations (main project: `CHANGES.md`, plugins: `plugins/CHANGELOG.md`).

Signed-off-by: Andrey Antukh <niwi@niwi.nz>

AGENTS.md

@@ -32,6 +32,17 @@ precision while maintaining a strong focus on maintainability and performance.
 5. When searching code, prefer `ripgrep` (`rg`) over `grep` — it respects
    `.gitignore` by default.
 
+## Changelogs
+
+The project has two changelogs:
+
+- **Main project changelog**: `CHANGES.md` (root of the repository). Tracks changes for the core Penpot application (backend, frontend, common, render-wasm, exporter, mcp).
+- **Plugins changelog**: `plugins/CHANGELOG.md`. Tracks changes for the plugins subproject only.
+
+When making changes, add a changelog entry to the appropriate file under the
+`## <version> (Unreleased)` section in the correct category
+(`:sparkles: New features & Enhancements` or `:bug: Bugs fixed`).
+
 ## GitHub Operations
 
 To obtain the list of repository members/collaborators:

CHANGES.md

@@ -10,6 +10,7 @@
 
 ### :bug: Bugs fixed
 
+- Fix incorrect invitation token handling on register process [Github #9380](https://github.com/penpot/penpot/pull/9380)
 - Fix incorrect handling of version restore operation [Github #9041](https://github.com/penpot/penpot/pull/9041)
 - Fix false “text editing” warning when applying tokens [Github #6346](https://github.com/penpot/penpot/issues/9346)