feat: one-click copy of effective auto-annotate params (REQ-186)

- ClassParamsTable: Copy button above per-class overrides table —
  clipboard text, one line per class (class/conf/iou/minbox/container),
  effective values (override else global), present in both the
  per-batch and mass auto-annotate modals via the shared component
- clipboard.js: extract legacyCopy + copyText from ArchiveControls
  (insecure-context execCommand fallback), ArchiveControls now imports it
- docs: REQ-186 added; design/ui-spec/tasks synced

docs/requirements.md

@@ -135,6 +135,14 @@ changes.
   without examples contribute nothing while any example exists, and clearing the last example
   restores the plain full-set preview. The preview and the batch job still use the same
   thresholds and per-class overrides.
+- **REQ-186** — The auto-annotate parameters table has a **copy button** that puts every
+  selected class's effective settings on the clipboard as short text, one class per line:
+  `class <name> conf <v> iou <v> minbox <v> container <true|false>`. Effective means the
+  per-class override where one is set, otherwise the global slider value; `container` is
+  the class's current checkbox state. The button sits in the shared per-class table, so it
+  exists in both the per-batch auto-annotate modal and the mass (batches tab) modal, and
+  the copied text is a plain baseline for later tuning — no structure beyond the line
+  format. Copying needs no network round-trip and never changes any setting.
 
 ## E. Review & correction