Dimension tool: both ends of a dimension follow the art it measures

A linear dimension clicked from an anchor to a point that is not an
anchor (a point on a segment, or a point a Smart Guide gave) followed
the art at the anchor end only, so scaling the art turned it into a
long slanted dimension.

- A point on a segment is stored by its curve parameter on that
  segment, and stays on it when the segment's anchors or handles are
  edited.
- Any other point is stored against anchors (and, for a path whose
  anchors lie on one line, handles) of the path under it, or of the
  path at the other end, and moves, scales, turns and reflects with
  that path. Beside a path whose anchors and handles all lie on one
  line, such as a straight line, it keeps its distance along and
  across the path: a reflection moves it as a half turn does, and a
  scale that is not uniform moves it as a uniform scale does.
- When linked art is reflected, a linear dimension's line goes to the
  reflected side, except for art whose anchors and handles lie on one
  line.
- Deleting the art, changing its anchor count or whether it is closed,
  turning an angle's arm into a curve, or making a measured circle or
  arc no longer circular leaves the dimension where it was, no longer
  linked, instead of removing it. Undo links it again.

Docs: docs/dimensions.md, docs/target-app-parity.md.

docs/dimensions.md

@@ -6,7 +6,13 @@ The **Dimension Tool** is in the Modify section of the toolbar. Its strip offers
 - **Linear:** hover a path segment and drag outwards: releasing places the dimension. Or click two
   points (anchors snap, Shift constrains to 45°), then click to place. A click within 8 pixels of
   an anchor of any path, in groups and compound paths too, takes that anchor, and the dimension
-  stays linked to it. A press on an anchor picks it when the pointer moves less than 8 pixels
+  stays linked to it. A point on a segment stays at its place along the segment, also when the
+  segment's anchors or handles are edited. Any other point is linked to the path under it, or,
+  with no path under it, to the path at the other end, and moves, scales, turns and reflects with
+  that path. Beside a path whose anchors and handles all lie on one line, such as a straight line,
+  the point keeps its distance along and across the path: a reflection moves it as a half turn
+  does, and a scale that is not uniform changes its distance across the path in proportion to the
+  path's length. A press on an anchor picks it when the pointer moves less than 8 pixels
   before the release; a longer drag drags out the dimension of the segment under the pointer. A
   curved segment is measured from end to end. With Smart Guides on, both points also snap into line with other objects'
   anchors and centres, and the second onto the construction guides through the first; the guides
@@ -52,10 +58,15 @@ position and alignment; changing one changes that dimension. **Apply to All** gi
 dimension in the document its style; **Set as Default** makes it the style of new dimensions.
 
 Measurements follow the art they measure through moves, scaling and anchor and handle edits,
-undo and redo included. Deleting the art, or changing its number of anchors or whether it is
-closed, removes its dimensions in the same undo step rather than attaching them to a different
-edge. A linked dimension moved on its own stays where it was dropped (its distance from the art
-changes); moved together with its art, it keeps its distance.
+undo and redo included. When the art is reflected, the line of a linked linear dimension goes to
+the reflected side, as far past the outermost point as before. This does not happen for art whose
+anchors and handles all lie on one line, such as a straight line, which a half turn puts in the
+same place as a reflection. Deleting the art, changing its number of anchors or whether it is
+closed, turning an angle's arm into a curve, or making a measured circle or arc no longer circular
+leaves its dimensions where they were, no longer linked, in the same undo step, rather than
+attaching them to a different edge. Undo links them again. A linked dimension moved on its own
+stays where it was dropped (its distance from the art changes); moved together with its art, it
+keeps its distance.
 
 Native `.vectorcraft` files keep the recipes and links. SVG, PDF and bitmap output contain
 ordinary paths and text, so exported dimensions look the same. Ungrouping a dimension leaves its

docs/target-app-parity.md

@@ -565,6 +565,7 @@ since 2026-10-01.
 **Drawing tools — Polygon and Star counts:** The existing canvas placement dialog reads the stored count and saves it only after successful placement. `polygon_and_star_canvas_counts_persist_without_new_toolbar_dialogs` covers both tools, repeated drags, tool switching, reopening and Cancel. Counts remain session tool options. Existing click and toolbar gestures are retained; no score or hour change.
 **Drawing tools, Star inner radius held with Ctrl/Cmd:** While a star is dragged out, Ctrl/Cmd keeps the inner radius the star showed when the key went down, also when the key is pressed with the pointer still. `a_star_drag_holds_its_inner_radius_with_ctrl_and_straightens_with_alt` and `a_star_drag_holds_the_inner_radius_it_shows_when_ctrl_goes_down` cover it, with Alt's straight shoulders and a drag canceled with Escape.
 **Drawing tools, Dimension tool horizontal and vertical linear dimensions:** A linear dimension between two clicked points or dragged out from a segment is aligned, horizontal or vertical, chosen by where the pointer moves while it is placed, and a click again by the second point gives aligned; `dimension.create` and `dimension.update` take `orientation`, and the dimension stays linked to the anchors it measures, keeps its orientation when it or the art turns, with a line that lay outside the points kept outside them; an unlinked horizontal or vertical dimension that is reflected has its line on the reflected side. `the_pointer_chooses_aligned_horizontal_or_vertical`, `two_points_measure_horizontally_vertically_or_aligned`, `clicking_again_by_the_second_point_places_an_aligned_dimension`, `a_segment_drag_measures_horizontally_vertically_or_aligned`, `points_on_a_vertical_line_measure_aligned`, `horizontal_and_vertical_dimensions_draw_lines_along_their_axis`, `turned_horizontal_dimensions_stay_horizontal`, `a_linked_horizontal_dimension_keeps_its_gap_from_turned_art`, `a_linked_horizontal_dimension_below_or_between_its_points_follows_turned_art`, `a_reflected_horizontal_dimension_keeps_its_line_on_the_reflected_side`, `a_dimension_without_an_orientation_reads_as_aligned`, `dimension_orientation_is_checked` and `a_turned_dimension_keeps_its_line_on_its_side` cover it.
+**Drawing tools, Dimension tool points that are not anchors follow the art:** A clicked point on a segment stays at its place along the segment, also when the segment curves, and a point off the art is linked to anchors (or, when the anchors lie on one line, anchors and handles) of the path, so both ends of the dimension follow when the art is moved, scaled, turned or reflected, also when the point was placed by a Smart Guide and when the dimension is saved and opened again; a linked linear dimension of reflected art (other than art on one line) has its line on the reflected side; deleting the art, changing its anchor count or whether it is closed, turning an angle's arm into a curve, or making a measured circle or arc no longer circular leaves the dimension where it was, no longer linked, instead of removing it. `a_dimension_to_a_point_on_a_segment_follows_the_art_at_both_ends`, `a_dimension_to_a_point_off_the_art_moves_with_the_art`, `a_dimension_whose_art_changes_its_anchors_stays_where_it_was`, `a_dimension_whose_art_is_opened_stays_where_it_was`, `angle_and_arc_dimensions_whose_art_no_longer_fits_stay_where_they_were`, `a_dimension_that_cannot_be_drawn_again_keeps_its_art`, `a_linked_dimension_of_reflected_art_has_its_line_on_the_reflected_side`, `a_dimension_to_a_point_off_a_line_follows_the_line`, `a_point_off_an_arch_is_reflected_with_the_arch`, `a_point_beside_an_almost_straight_curve_follows_it`, `a_point_off_a_loop_with_its_anchors_in_one_place_follows_it`, `a_point_beside_a_reflected_line_moves_as_a_half_turn_would`, `a_point_on_a_segment_stays_on_it_when_the_segment_curves`, `a_linked_dimension_of_a_reflected_curve_has_its_line_on_the_reflected_side`, `a_dimension_of_art_reflected_across_its_points_changes_sides`, `a_dimension_between_paths_reflected_each_in_its_own_way_keeps_its_offset`, `free_points_survive_a_native_file`, `dimension_free_points_are_checked`, `points_off_anchors_are_held_against_the_path` and `a_point_smart_guides_place_is_held_against_the_path` cover it.
 **Live trace result bounds and selection highlights exclude the retained bitmap except in source-image views:** `live_trace_result_bounds_exclude_the_retained_bitmap_at_any_angle` checks every TraceView, geometric and visual bounds and rotated result bounds. `live_trace_selection_highlight_excludes_the_retained_source_rectangle` checks result highlights and the existing ordinary-group policy. Shared editing-child traversal also preserves Shaper handling.
 **Artboard Options shares existing presets and orientation controls and can fit artwork without moving it; artwork fitting includes all drawn document art across artboards and off-board; artwork bounds are cached by active document and revision, and selection uses the shared bounds cache across artboards:** Shared existing preset definitions are reused; no external preset assets are added. Presets preserve each selected artboard's orientation, and orientation choices apply even when the active board already matches. Fit operations draft bounds until OK, affect only the active artboard and leave artwork in place. Regression coverage checks draft/Cancel, selected-set application, active-only fitting and Undo.