OpenType: the panel's Position menu sets superscript, subscript, numerator or denominator glyphs

The OpenType panel gets a Position menu after Figure, with Default
Position, Superscript, Subscript, Numerator and Denominator. `numr` and
`dnom` join the extra features (the existing bits keep their indices),
so they round-trip through the stored tags and reach the shaper.

text.setStyle and text.setRangeStyle take `featureChanges`, which turns
features on or off on top of each character's own features in one
command and keeps every tag the list does not name. The Figure menu,
the Position menu and the checkboxes send it, so on a selection whose
characters have different features each character keeps its other
features. Reset OpenType Features still sends `features`.

Catalog rows for Position:, Default Position, Numerator and
Denominator; one line each in docs/type-parity.md and
docs/target-app-parity.md.

docs/target-app-parity.md

@@ -865,6 +865,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
   The Every-line Composer composes a paragraph whose characters differ in line metrics (type size, font, leading or vertical scale, or an inline graphic taller than the text) in rectangular area type, rows and columns included. In area type of another shape, or with text wrap, such a paragraph is broken with the Single-line Composer.
   The Character panel's Small Caps, Superscript and Subscript buttons and the panel menu's items of the same names turn small caps and the superscript or subscript position on and off for the selected type, or for the text the Type tool has selected (`text.setFormat` or `text.setRangeStyle` `{smallCaps, position}`), in Document Setup's proportions. Turning Superscript on turns Subscript off, and turning Subscript on turns Superscript off. A button or item shows as on when the first selected character (at a caret, the character before it) has its attribute.
   The OpenType panel's Stylistic Alternates and Titling Alternates checkboxes turn `salt` and `titl` on and off for the selected type, and its Figure menu lists Default Figure, Tabular Lining, Proportional Lining, Proportional Oldstyle and Tabular Oldstyle; Proportional Lining sets `pnum` and `lnum` and turns `tnum` and `onum` off, Tabular Lining turns `pnum` off and keeps `lnum`, Proportional Oldstyle turns `lnum` off and keeps `pnum`, and Default Figure and Tabular Oldstyle turn `pnum` and `lnum` off. Behavior reference: [Format text with OpenType features](https://helpx.adobe.com/illustrator/desktop/design-with-text/special-characters-glyphs/format-text-with-opentype-features.html) and [Use swashes, titling alternates, or stylistic alternates](https://helpx.adobe.com/illustrator/desktop/design-with-text/special-characters-glyphs/use-swashes-titling-alternates-or-stylistic-alternates.html) (public documentation). Tests: `panels::opentype::tests`.
+  The OpenType panel's Position menu lists Default Position, Superscript, Subscript, Numerator and Denominator, as [Format text with OpenType features](https://helpx.adobe.com/illustrator/desktop/design-with-text/special-characters-glyphs/format-text-with-opentype-features.html) describes; Superscript, Subscript, Numerator and Denominator set `sups`, `subs`, `numr` and `dnom` for the selected type and turn the other three off, and Default Position turns all four off. The menu shows Mixed when the characters it acts on differ, and an entry chosen then applies to all of them. These two rules are VectorCraft's own, as is setting the feature on type whose font lacks the glyphs, which then draws unchanged. The panel's menus and checkboxes change only their own features on each selected character, so characters keep their other OpenType features (`text.setStyle` and `text.setRangeStyle` `{featureChanges}`). Tests: `panels::opentype::tests`, `features::tests::numerators_and_denominators_are_kept_and_shaped`.
 - **Paragraph alignment:** the shared Paragraph/Properties alignment row leaves every button unselected when the paragraphs it acts on differ. Auto resolves per paragraph; choosing an alignment uses the existing command. Headless paragraph_mixed_alignment_* regressions exercise mixed → Center → Undo, caret/uniform states, Unicode range boundaries, Auto/direction, split runs and grouped text. These regressions and full integration CI pass. Original captures confirm mixed → Center → Undo in the existing alignment-button layout. The [public Paragraph panel guide](https://helpx.adobe.com/illustrator/desktop/design-with-text/edit-format-text/paragraph-panel-overview.html) lists the seven controls, but does not specify mixed-state rendering. Other paragraph fields remain outside this change; scores and hours unchanged.
   For Auto Size area type in columns, the bisection for the frame's height runs on the lines of the one-column layout, and its result is checked with at most two layouts of the columns. When the text wraps around objects or does not fit the one-column layout, or when the check fails, the columns are laid out at every step of the bisection, as before. Typing at the start of a story of 50,000 characters in 2 columns took 1,670 ms a keystroke and now takes 292 ms (release build, `auto_height_in_columns_typing_timing`).
   Exports to PDF, EPS, SVG, EMF, WMF and the raster formats warn about the area type and type on a path that they draw without the text that doesn't fit, and give their ids, as Print and Print Preview do.

docs/type-parity.md

@@ -28,7 +28,7 @@ against Illustrator's public documentation; **estimated** unless noted.
 | Character and Paragraph panels, styles with overrides | done | Character-style Auto-leading resets, partial definitions, local leading overrides, override markers, Undo/Redo and native serialization have regression coverage; differing paragraph alignments leave the shared alignment buttons unselected (headless regressions, full integration CI and visual review pass); mixed-value display for other paragraph fields remains missing |
 | Character size and horizontal scale after object/group scaling | done | #1034: fields and setters compensate the stored affine; point size follows the transformed em-height axis, not the glyph ink bounds. Range edits, keyboard increments, leading and baseline shift use document points; rotation, reflection and shear remain editable. |
 | Preserve font sizes while scaling a group | missing | Separate enhancement; scaling still scales text with the other artwork. |
-| OpenType panel, Glyphs panel, alternates | done | Highlight Alternate Glyphs preference (#394, off by default) paints pink behind OpenType substitutions on screen when on (required shaping such as Arabic joining forms and the lam-alef ligature, including a lam-alef older fonts file under `liga`, is not highlighted; an optional feature that changes the ligature is); stylistic sets ss01–ss20, stylistic and titling alternates, proportional and lining figures, superscript and subscript are character-style features (`text.setStyle {features}`, #1607). The Glyphs panel highlights the character selected with the Type tool (a range's first character, else the one before the caret) and scrolls it into view as the selection moves (#4908; `panels::glyphs` tests); its Show menu lists Unicode ranges, and Alternates for Current Selection is not there yet |
+| OpenType panel, Glyphs panel, alternates | done | Highlight Alternate Glyphs preference (#394, off by default) paints pink behind OpenType substitutions on screen when on (required shaping such as Arabic joining forms and the lam-alef ligature, including a lam-alef older fonts file under `liga`, is not highlighted; an optional feature that changes the ligature is); stylistic sets ss01–ss20, stylistic and titling alternates, proportional and lining figures, superscript and subscript are character-style features (`text.setStyle {features}`, #1607); the OpenType panel's Position menu sets superscript, subscript, numerator or denominator glyphs (`sups`, `subs`, `numr`, `dnom`). The Glyphs panel highlights the character selected with the Type tool (a range's first character, else the one before the caret) and scrolls it into view as the selection moves (#4908; `panels::glyphs` tests); its Show menu lists Unicode ranges, and Alternates for Current Selection is not there yet |
 | Font menu: samples, live preview, filters, favourites, recent families; font matching by any name; Find Font | done | #3515: recently applied families appear first, once each; missing families are omitted and the existing Number of Recent Fonts setting applies; #339; script filter: Japanese, Latin, Thai; the font scan on Linux also reads the folders fontconfig's configuration lists, such as TeX fonts under `/usr/share/texmf/fonts` (#1548, fixes #1529; not verified on Linux) |
 | Missing glyphs set in an installed font made for their script (Thai, Lao, Khmer, Myanmar first; then any font that has them) | done | Thai: Leelawadee UI, Tahoma, Thonburi, Sukhumvit Set, Noto Sans Thai, TLWG |
 | Full font-name matching (OpenType name ID 4) | done | #1258: loaded/cataloged faces and Missing Fonts searches; localized names and variable default faces; Windows font-service QA pending |