M12: tag unstructured AcroForm widgets (#1451)

* M12: tag unstructured AcroForm widgets

* i18n: translate form tag command

* i18n: repair form-field label merges

* fix(i18n): refresh translation catalog hashes

* fix(i18n): preserve main translations after rebase

* Merge main; tag a widget listed on several pages once, docs say existing trees are extended

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Merge main; add the Vietnamese catalog entry for Tag form fields

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Brandon Thomas <echelon@gmail.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

parity/acrobat-features.toml

@@ -8876,11 +8876,11 @@ title = "Autotag form fields"
 area = "M"
 tier = "P1"
 milestone = "M12"
-status = "planned"
-commands = []
-tools = []
-evidence = []
-notes = ""
+status = "partial"
+commands = ["a11y.autotag_fields"]
+tools = ["accessibility_autotag_form_fields"]
+evidence = ["crates/a11y/src/tests.rs::autotag_form_fields_writes_widget_structure_and_parent_tree", "crates/automation/tests/automation.rs::autotag_form_fields_writes_reviewable_widget_tags"]
+notes = "For an untagged AcroForm, writes Form structure elements, OBJR references, widget StructParent keys and ParentTree entries. An existing tree is extended when its root points directly to a Document element and its ParentTree uses a direct Nums array; other layouts are refused before any edit. A widget listed on several pages is tagged once. Text, figures, links and other content remain untagged."
 
 [[feature]]
 id = "a11y.reading-order-tool"