Add test instance post-import validation

AGENTS.md

@@ -10,7 +10,8 @@ environment. The canonical plugin sources live in `plugins/`:
 - `plugins/redmine_contacts_helpdesk/` - patched RedmineUP Helpdesk fork.
 
 Top-level Python helpers such as `redmine_outbox_worker.py` and
-`reset_helpdesk_mail_settings.py` support LAN test-instance operations. Project
+`reset_helpdesk_mail_settings.py` support LAN test-instance operations.
+`validate_test_instance.py` performs read-only post-import checks. Project
 notes and design records live in `docs/`. `redMCP/` contains the PHP
 Redmine API/MCP wrapper. `dist/*.MANIFEST.md` files are tracked; rollback
 tarballs are intentionally ignored. `redmine-copy/` is an ignored
@@ -24,7 +25,7 @@ Use targeted syntax checks before committing:
 ruby -c plugins/redmine_contacts/lib/redmine_contacts/utils/check_mail.rb
 ruby -c plugins/redmine_contacts_helpdesk/app/models/helpdesk_mailer.rb
 ruby -c plugins/redmine_event_outbox/lib/redmine_event_outbox.rb
-python3 -m py_compile redmine_outbox_worker.py reset_helpdesk_mail_settings.py
+python3 -m py_compile redmine_outbox_worker.py reset_helpdesk_mail_settings.py validate_test_instance.py
 cd redMCP && php -l app/RedmineClient.php && composer validate
 ```
 
@@ -32,6 +33,7 @@ Dry-run operational helpers before applying changes:
 
 ```sh
 ./reset_helpdesk_mail_settings.py --dry-run
+./validate_test_instance.py
 ./redmine_outbox_worker.py --dry-run --batch-size 10
 ```
 
@@ -48,7 +50,8 @@ Prefer focused checks over broad legacy test runs unless changing shared plugin
 behavior. For mail or database helpers, validate with dry runs first, then test
 against the LAN Redmine copy using controlled projects such as `fud-helpdesk` or
 `fud-nohelpdesk`. Record notable manual validation in `docs/` when behavior or
-deployment assumptions change.
+deployment assumptions change. The post-import workflow lives in
+`docs/test_instance_post_import.md`.
 
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