M6: tests for where a list starts counting, through the issue's own steps (#2273)

The engine test now follows the issue: a list typed at 5, saved as .fig and opened, split by Backspace at the start of "b". The REST fixture is a top-level list, the junk sweep reaches the new loop through a listed text layer, and the document crate tests the new rule for nested, bullet, plain and over-deep levels. ParaList gets its doc comment back, and the revision row names the item written with 0.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Model-Effort: Opus 5.5 drove; Fable 5.2 queued; Opus 5.5 briefed; Sonnet 5.5 wrote at medium

docs/file-format-parity.md

@@ -196,7 +196,7 @@ scales and empty-style clears; they have not been checked in other software.
 
 | Date | Change | Summary |
 |---|---|---|
-| 2026-11-12 | patch | M6, #2273: `.fig` import: a numbered list keeps its start only on the item where it starts counting. Figma writes the start on every line of the list (measured in Figma's web app, 2026-11-12, from a saved .fig: a list started at 5 has `listStartOffset` 4 on all its lines, and the item split off by Backspace is written with 0), so reading every line's value restarted the items after a split at the old start. The export is unchanged and a re-import now equals what went in; REST `listStartOffsets` read the same way |
+| 2026-11-12 | patch | M6, #2273: `.fig` import: a numbered list keeps its start only on the item where it starts counting. Figma writes the start on every line of the list (measured in Figma's web app, 2026-11-12, from a saved .fig: a list started at 5 has `listStartOffset` 4 on all its lines, and after Backspace takes a middle item out of the list, the item after it starts a new list and is written with 0), so reading every line's value restarted the items after a split at the old start. The export is unchanged and a re-import now equals what went in; REST `listStartOffsets` read the same way |
 | 2026-11-10 | minor | M4, #2222: a boolean group's corner radius and smoothing are read and written by the `.fig` importer and exporter, and by the REST importer |
 | 2026-11-07 | patch | Fonts, #2092: a font loaded with `text.loadFont` is the counterpart of a font uploaded to the organization, which Figma's help center ("Manage conflicting fonts") ranks first, ahead of installed fonts and the web fonts. FigCraft chose the first face added for a family and style, so the built-in Inter 4.x kept Regular, SemiBold and Bold after Inter 3.19 was loaded and only Medium refitted. A loaded face now wins over the other faces of its family and style, the latest load over earlier ones; style matching and fallbacks are unchanged, and `refitted` lists the text whose size changes. Installed versus built-in order is not changed here. Test: `fontdb::tests::a_loaded_face_wins_over_the_built_in_one_of_its_family_and_style`. Numbers unchanged. |
 | 2026-11-08 | minor | M6, #2097 follow-up: per-point vector corner radii take the scale of the row supplying `vectorData`, including nested instance rows; override and derived rows are not scaled twice. Network caching distinguishes the instance scale even when resizing gives two vectors the same final box. Synthetic tests cover missing/unit factors, half/double scale, derived size alone, overridden and derived vector data, nested scale and equal-size cache separation. Layer-radius fallback remains the separate #2115 change. Numbers unchanged. |