Add outbox worker processing policy

docs/redmineup_local_fork_changelog.md

@@ -30,7 +30,37 @@ environment. Before risky edits, archive the current plugin directories in
   - Helpdesk outbox/worker validation now has a repeatable live script.
 - Next meaningful milestone:
   - Run `validate_helpdesk_outbox_worker.py` after outbox or worker changes,
-    then choose the external index target and durable processing policy.
+    then choose the external index target.
+
+## 2026-04-25 - Outbox Worker Processing Policy
+
+- Touched areas:
+  - External outbox worker
+  - Worker operations documentation
+- Purpose:
+  - Make the worker usable for bounded JSONL publishing before a message bus is
+    chosen.
+  - Add queue visibility and explicit processed-row cleanup for test-instance
+    maintenance.
+- Behavior changed:
+  - Default worker output is `/tmp/redmine-outbox/derived_documents.jsonl`.
+  - `--status` reports pending, ready, locked, failed, and processed counts.
+  - `--purge-processed-days N` previews processed-row cleanup; `--apply-purge`
+    is required to delete rows.
+  - Normal processing still marks rows processed only after successful output.
+- LAN test result:
+  - `./redmine_outbox_worker.py --status` reported 100 total rows, 100 ready,
+    0 locked, 0 failed, and 0 processed before the processing run.
+  - `./redmine_outbox_worker.py --dry-run --batch-size 5` previewed the first
+    five rows without marking them processed.
+  - `./redmine_outbox_worker.py --batch-size 5` processed five rows and wrote
+    six JSONL documents to `/tmp/redmine-outbox/derived_documents.jsonl`.
+  - Follow-up status reported 95 pending, 95 ready, 0 locked, 0 failed, and
+    5 processed.
+  - `./redmine_outbox_worker.py --purge-processed-days 30` previewed zero rows.
+  - Follow-up `./validate_helpdesk_outbox_worker.py` passed with controlled
+    Helpdesk issue `#39875`; final status reported 118 total rows, 113 ready,
+    0 locked, 0 failed, and 5 processed.
 
 ## 2026-04-25 - Helpdesk Outbox Worker Validation