feat(manual-batch): canonical plate + manual mode as default

- canonical_plate (uppercase alnum, strips space/dot/hyphen) at all plate
  write sites; pretty_plate for render (history, XLSX, operator tile) so
  B 1234 XYZ and B1234XYZ are one plate everywhere
- group_dos_by_plate compares canonical plates -> no false mixed_plates
- warn-only (never blocking) plate format hint in operator + monitoring modals
- batch.default_mode: manual (auto merged truck loads when a sack sat in the
  counting ROI); operator banner explains plate -> start -> stop
- docs + AGENTS known-limitation note; 85 tests pass

AGENTS.md

@@ -35,7 +35,10 @@ Indonesian (`karung`=sack, `truk`=truck); YOLO class names are English
   `LOCAL_RTSP`) is deprecated — don't add keys there. Dashboard mode switches
   write `config.yaml` `models.active_mode` (atomic, manual restart to apply);
   `batch_mode.json` keeps only batch flow mode (`auto`|`do_manual`|`manual`,
-  default seed `batch.default_mode: auto`).
+  default seed `batch.default_mode: manual`). `manual` start requires plate
+  (`canonical_plate`: spaces/dots/hyphens stripped, upper; DB stores canonical,
+  render `pretty_plate`); `auto` merges batches when a sack sits in the counting
+  ROI — known limitation, fix not landed.
   **Port split:** `mode` / `model_mode` / `require_plate` / `require_do` POSTs →
   office `:5721` only (403 on `:5000`); **`ocr_engine` office-only too**
   (default `rapid`). Discard batch only if both **gross** `count==0` and