Forms: fields listed only as page widgets join the form (#649)

A PDF whose AcroForm /Fields array is empty or missing listed no
fields, so none were fillable even though every widget sat on a page
with its name and value: Acrobat and the browsers fill those. The page
widgets are now adopted as fields — after the tree-listed ones, through
each widget's topmost unlisted /Parent so a field split across several
widgets stays one — and the leniency is recorded, never silent.

- forms: fields() walks /Fields as before, then adopts the unlisted
  page widgets; adopted_page_fields() counts them for the note.
- render: the inspector's field list adopts them the same way, so the
  Fields panel, the field-count notice and menu gating follow.
- engine: opening such a file notes "the form's /Fields list omits N
  fields; they were read from the page annotations" in the repair log
  (Document Properties ▸ Advanced).

Co-authored-by: GLM-5.3 <noreply@z.ai>
Co-authored-by: Brandon Thomas <echelon@gmail.com>

parity/acrobat-features.toml

@@ -4302,8 +4302,8 @@ milestone = "M3"
 status = "shipped"
 commands = ["form.fields"]
 tools = ["doc_info"]
-evidence = ["crates/ui-egui/tests/view.rs::field_list_jumps_to_a_fields_page"]
-notes = "read-only list with jump-to-field; filling and editing are separate features (M6)"
+evidence = ["crates/ui-egui/tests/view.rs::field_list_jumps_to_a_fields_page", "crates/render/src/inspect.rs::fields_listed_only_on_the_pages_are_listed"]
+notes = "read-only list with jump-to-field; filling and editing are separate features (M6); fields a file lists only as page widgets (empty /Fields) are adopted too"
 
 [[feature]]
 id = "form.highlight-fields"
@@ -4338,7 +4338,7 @@ milestone = "M6"
 status = "shipped"
 commands = ["form.fields"]
 tools = ["form_fill", "form_fields"]
-evidence = ["crates/ui-egui/tests/forms.rs::typing_into_a_text_field_and_tabbing_on", "crates/forms/src/tests.rs::text_fields_get_new_appearances", "crates/engine/src/tests.rs::filling_a_form_shows_saves_and_undoes"]
+evidence = ["crates/ui-egui/tests/forms.rs::typing_into_a_text_field_and_tabbing_on", "crates/forms/src/tests.rs::text_fields_get_new_appearances", "crates/engine/src/tests.rs::filling_a_form_shows_saves_and_undoes", "crates/automation/tests/automation.rs::orphan_form_fields_through_tools"]
 notes = "in-place editor; Enter or clicking away commits, Escape cancels; no format/keystroke JavaScript yet (M6.4)"
 
 [[feature]]