Drawn signatures and drawings resize from their handles (#920)

A drawn Fill & Sign signature is an Ink annotation, and Ink couldn't be
resized: the Select tool showed no handles and the engine refused
ResizeAnnotation ("Ink comments can't be resized"). Typed and image
signatures (stamps) already resize (#335, #355), so drawn ones were the
gap left in #331.

- annot: set_rect scales an Ink annotation's strokes into the new
  rectangle, keeping each side's margin between the strokes and /Rect
  so the line isn't clipped, and regenerates the appearance. A straight
  stroke with no extent on one axis is centred on it.
- ui-egui: Ink is resizable with the 8 handles. A drawn signature's
  corners keep its shape, as image signatures' do; other drawings resize
  freely like shapes.

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

parity/acrobat-features.toml

@@ -3638,8 +3638,8 @@ milestone = "M5"
 status = "shipped"
 commands = ["comment.ink"]
 tools = ["comment_add"]
-evidence = ["crates/ui-egui/tests/comments.rs::shapes_and_ink_are_drawn_by_dragging", "crates/annot/src/tests.rs::ink_strokes_are_smooth_curves_through_their_points"]
-notes = "one ink annotation per stroke; strokes are drawn as smooth curves through their points, as in Acrobat"
+evidence = ["crates/ui-egui/tests/comments.rs::shapes_and_ink_are_drawn_by_dragging", "crates/annot/src/tests.rs::ink_strokes_are_smooth_curves_through_their_points", "crates/annot/src/tests.rs::drawings_resize_by_scaling_their_strokes"]
+notes = "one ink annotation per stroke; strokes are drawn as smooth curves through their points, as in Acrobat; resize with the 8 handles (the strokes scale into the new box)"
 
 [[feature]]
 id = "comment.eraser"
@@ -5250,6 +5250,7 @@ milestone = "M5"
 status = "shipped"
 commands = ["sign.fill.signature", "sign.fill.initials", "sign.fill.signature.change", "sign.fill.initials.change", "sign.fill.signature.remove", "sign.fill.initials.remove"]
 tools = ["fill_sign_add", "comment_edit", "comment_image_preview"]
+evidence = ["crates/ui-egui/tests/fill_sign.rs::drawn_signatures_resize_from_their_corners", "crates/ui-egui/tests/fill_sign.rs::drawn_and_typed_signatures_stay_upright_on_rotated_pages", "crates/automation/tests/automation.rs::typed_signatures_stay_upright_on_rotated_pages", "crates/ui-egui/tests/fill_sign.rs::image_signature_corners_restore_original_aspect_after_edge_resize_and_reopen", "crates/ui-egui/src/comments.rs::proportional_corners_keep_the_opposite_anchor_and_edges_stretch_one_axis", "crates/ui-egui/tests/fill_sign.rs::image_signature_live_resize_and_move_preserve_background_and_hide_moving_handles", "crates/ui-egui/tests/fill_sign.rs::embedded_image_signature_live_gestures_follow_document_and_view_rotation", "crates/automation/tests/automation.rs::image_signature_preview_layers_are_read_only_and_survive_encrypted_save", "crates/engine/src/signature_image.rs::embedded_signature_preview_preserves_alpha_without_editing_the_document", "crates/engine/src/signature_image.rs::oversized_embedded_signature_preview_is_rejected_before_decoding", "crates/ui-egui/tests/fill_sign.rs::image_signature_preview_follows_pointer_at_page_size_with_zoom_and_rotation", "crates/ui-egui/tests/fill_sign.rs::image_signature_placement_selects_resize_handles_and_requires_reselecting_to_repeat", "crates/ui-egui/tests/fill_sign.rs::typed_signatures_and_initials", "crates/ui-egui/tests/fill_sign.rs::signing_draws_a_signature_once_and_places_it", "crates/ui-egui/tests/fill_sign.rs::changing_saved_signatures_and_initials_preserves_placed_marks", "crates/ui-egui/tests/fill_sign.rs::changing_drawn_signatures_can_be_cancelled_or_switched_to_type", "crates/ui-egui/tests/fill_sign.rs::saved_signature_cards_remove_and_add_without_changing_the_document", "crates/ui-egui/tests/fill_sign.rs::long_typed_names_fit_the_placed_signature_and_keep_every_outline", "crates/ui-egui/src/fill_sign.rs::long_signature_previews_have_clear_margins", "crates/ui-egui/tests/control.rs::saved_signature_can_be_changed_through_the_control_channel", "crates/fonts/src/script.rs::a_name_becomes_outlines", "crates/fonts/src/script.rs::long_names_keep_every_glyph_with_bounded_outline_work", "crates/automation/tests/automation.rs::fill_and_sign_through_tools", "crates/ui-egui/tests/fill_sign.rs::image_signatures_and_initials_can_be_imported_placed_and_remembered", "crates/ui-egui/tests/fill_sign.rs::image_import_cancel_clear_and_errors_preserve_saved_signatures", "crates/engine/src/signature_image.rs::image_signatures_preserve_alpha_and_fit_the_signature_box", "crates/engine/src/signature_image.rs::invalid_and_oversized_signature_images_are_rejected", "crates/engine/src/signature_image.rs::jpeg_signatures_are_normalized_to_png", "crates/engine/src/signature_image.rs::jpeg_signature_orientation_is_applied_before_preview_and_embedding", "crates/engine/src/signature_image.rs::very_wide_image_signatures_keep_the_requested_rectangle", "crates/automation/tests/automation.rs::image_signatures_through_tools_preserve_transparency_and_survive_save", "crates/ui-egui/tests/fill_sign.rs::fill_and_sign_tools_pick_up_placed_marks_to_move_and_resize_them"]
 evidence = ["crates/ui-egui/tests/fill_sign.rs::select_tool_picks_up_a_signature_over_a_form_field", "crates/ui-egui/tests/fill_sign.rs::drawn_and_typed_signatures_stay_upright_on_rotated_pages", "crates/automation/tests/automation.rs::typed_signatures_stay_upright_on_rotated_pages", "crates/ui-egui/tests/fill_sign.rs::image_signature_corners_restore_original_aspect_after_edge_resize_and_reopen", "crates/ui-egui/src/comments.rs::proportional_corners_keep_the_opposite_anchor_and_edges_stretch_one_axis", "crates/ui-egui/tests/fill_sign.rs::image_signature_live_resize_and_move_preserve_background_and_hide_moving_handles", "crates/ui-egui/tests/fill_sign.rs::embedded_image_signature_live_gestures_follow_document_and_view_rotation", "crates/automation/tests/automation.rs::image_signature_preview_layers_are_read_only_and_survive_encrypted_save", "crates/engine/src/signature_image.rs::embedded_signature_preview_preserves_alpha_without_editing_the_document", "crates/engine/src/signature_image.rs::oversized_embedded_signature_preview_is_rejected_before_decoding", "crates/ui-egui/tests/fill_sign.rs::image_signature_preview_follows_pointer_at_page_size_with_zoom_and_rotation", "crates/ui-egui/tests/fill_sign.rs::image_signature_placement_selects_resize_handles_and_requires_reselecting_to_repeat", "crates/ui-egui/tests/fill_sign.rs::typed_signatures_and_initials", "crates/ui-egui/tests/fill_sign.rs::signing_draws_a_signature_once_and_places_it", "crates/ui-egui/tests/fill_sign.rs::changing_saved_signatures_and_initials_preserves_placed_marks", "crates/ui-egui/tests/fill_sign.rs::changing_drawn_signatures_can_be_cancelled_or_switched_to_type", "crates/ui-egui/tests/fill_sign.rs::saved_signature_cards_remove_and_add_without_changing_the_document", "crates/ui-egui/tests/fill_sign.rs::long_typed_names_fit_the_placed_signature_and_keep_every_outline", "crates/ui-egui/src/fill_sign.rs::long_signature_previews_have_clear_margins", "crates/ui-egui/tests/control.rs::saved_signature_can_be_changed_through_the_control_channel", "crates/fonts/src/script.rs::a_name_becomes_outlines", "crates/fonts/src/script.rs::long_names_keep_every_glyph_with_bounded_outline_work", "crates/automation/tests/automation.rs::fill_and_sign_through_tools", "crates/ui-egui/tests/fill_sign.rs::image_signatures_and_initials_can_be_imported_placed_and_remembered", "crates/ui-egui/tests/fill_sign.rs::image_import_cancel_clear_and_errors_preserve_saved_signatures", "crates/engine/src/signature_image.rs::image_signatures_preserve_alpha_and_fit_the_signature_box", "crates/engine/src/signature_image.rs::invalid_and_oversized_signature_images_are_rejected", "crates/engine/src/signature_image.rs::jpeg_signatures_are_normalized_to_png", "crates/engine/src/signature_image.rs::jpeg_signature_orientation_is_applied_before_preview_and_embedding", "crates/engine/src/signature_image.rs::very_wide_image_signatures_keep_the_requested_rectangle", "crates/automation/tests/automation.rs::image_signatures_through_tools_preserve_transparency_and_survive_save", "crates/ui-egui/tests/fill_sign.rs::fill_and_sign_tools_pick_up_placed_marks_to_move_and_resize_them"]
 notes = "signature and initials, typed (Dancing Script outlines as filled paths, no font embedded), drawn or imported from local PNG/JPEG images; all three are placed upright and anchored as displayed on pages with /Rotate (#299); saved in settings with preview cards and add/change/remove controls; changes leave placed annotations untouched; images preserve alpha, aspect ratio and EXIF orientation, fit within 150 pt by 32 pt (24 pt for initials), and are normalized without source paths or metadata; image previews follow the pointer at placement size with zoom and rotation; signatures/initials place once then select the new annotation; while a Fill & Sign tool is active, marks already placed are picked up as with Select (hover shows the move cursor, a click selects, a drag moves, the selected mark's handles resize) and the tool places only away from them; embedded image signatures resize and move live, hiding the frame during movement and restoring it on release; corner handles preserve the original aspect ratio of the embedded image with the opposite corner anchored, while edge midpoint handles stretch width or height independently; cached background layers preserve page content and alpha, including reopened/encrypted documents; Escape cancels a gesture without committing; stamps resize through selection handles or comment_edit with their original appearance; native and web asynchronous pickers; fill_sign_add accepts path instead of text; image imports capped at 4 MiB, 4 megapixels and 4096 pixels per side"