M10: Edit reads only a page with no text of its own

Review of #1609: the Edit-triggered recognition also read pages that have real
text (a flyer or slide export with a full-page background picture), adding an
undo step and marking the file modified just because Edit was turned on.

It now runs with skip_text_pages on, so such a page is left alone. A new
OcrSettings::native_text_only decides what counts as the page's text: its own
content and form fields, not comments and text boxes (which are also not drawn
into the picture that is read), so a scan with a few comments on it is still a
scan, as in Acrobat. The doc comment now says what the code does.

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

parity/acrobat-features.toml

@@ -6517,7 +6517,7 @@ status = "partial"
 commands = ["edit.edit_text"]
 tools = ["text_edit"]
 evidence = ["crates/engine/tests/ocr_edit.rs::editing_an_ocr_word_covers_the_scan_and_shows_the_new_text", "crates/engine/tests/ocr_edit.rs::an_explicit_colour_is_kept_for_the_new_text", "crates/engine/tests/ocr_edit.rs::ocr_words_group_into_phrases_that_edit_in_place", "crates/engine/tests/ocr_edit.rs::a_longer_ocr_phrase_grows_rightwards", "crates/engine/tests/ocr_edit.rs::a_rewritten_ocr_phrase_keeps_its_word_widths", "crates/ui-egui/tests/ocr.rs::an_ocr_word_opens_for_editing_and_stays_open", "crates/ui-egui/tests/ocr.rs::editing_a_scanned_page_recognizes_its_text_first_and_only_once"]
-notes = "On demand, per edit: in Edit text & images, recognised text (the invisible OCR layer over a scan) is grouped into phrases (words across a word space; a wider gap such as a table cell, and each scanned line, stay separate) and opens for editing on a click. Applying draws the new text visibly in the scan's sampled ink colour (or the chosen one) and first covers the old words with the paper colour sampled around them, so the scanned word no longer shows; the phrase keeps each word's position and width and grows rightwards instead of wrapping. Turning Edit text & images on for a scanned page (an image covering at least half of a page that has no text, once per page per window; one undoable \"Recognize text\" step) now recognizes its words first, as Acrobat's \"Converting scanned page to Editable Text and Images\" does (English only until more OCR languages exist, gap 7). Still missing: separating the photographs on the page from the lettering, matching the scanned typeface (the layer's Helvetica is used), and covering on a textured or patterned background (one flat colour is used)."
+notes = "On demand, per edit: in Edit text & images, recognised text (the invisible OCR layer over a scan) is grouped into phrases (words across a word space; a wider gap such as a table cell, and each scanned line, stay separate) and opens for editing on a click. Applying draws the new text visibly in the scan's sampled ink colour (or the chosen one) and first covers the old words with the paper colour sampled around them, so the scanned word no longer shows; the phrase keeps each word's position and width and grows rightwards instead of wrapping. Turning Edit text & images on for a scanned page (an image covering at least half of a page that has no text of its own, once per page per window; comments and text boxes over it do not count as text, a page with real text and a background picture is left alone; one undoable \"Recognize text\" step) now recognizes its words first, as Acrobat's \"Converting scanned page to Editable Text and Images\" does (English only until more OCR languages exist, gap 7). Still missing: separating the photographs on the page from the lettering, matching the scanned typeface (the layer's Helvetica is used), and covering on a textured or patterned background (one flat colour is used)."
 
 [[feature]]
 id = "ocr.ocr-downsample"