.ai import: legacy type keeps its tab stops

A tab definition in type of the legacy format (`numDots numTabs Xb`, a
`leader decimal tabType tabPosition Xe` for each stop, then `XB`) was
skipped, so every paragraph opened with only the default stops every
36 pt. The stops it describes now become the paragraph's tab stops
(left, center, right or decimal, at their positions), and they last
into the next paragraphs and text objects like the other paragraph
attributes. A definition with no stops, or whose descriptions were all
skipped, leaves the default ones. A description with an unknown type or
a position outside 0 to 100000 pt is skipped, and so is one past the
first 1024 of a definition. A text object's `To` ends a definition that
an earlier object left open.

Docs: docs/file-format-parity.md.

docs/file-format-parity.md

@@ -125,8 +125,9 @@ private editing data. VectorCraft:
   and word spacing (`TC`, `TW`), hanging punctuation (`Tq`) and hyphenation (`Th`). Its type in a font
   re-encoded with encoding pairs of its own (`TZ`) is decoded with those pairs, and with the file's encoding
   (`TE`) for the codes they leave out unless the `TZ` sets `useDefault` to 0. Its patterns in
-  and word spacing (`TC`, `TW`), hanging punctuation (`Tq`) and hyphenation (`Th`); its special characters
-  (`TS`) join the story, and end render (`Te`) and pop text matrix (`TM`) are read and ignored. Its patterns in
+  and word spacing (`TC`, `TW`), hanging punctuation (`Tq`) and hyphenation (`Th`); its tab definitions
+  (`Xb` … `XB`) set its paragraphs' tab stops; its special characters (`TS`) join the story, and end render
+  (`Te`) and pop text matrix (`TM`) are read and ignored. Its patterns in
   the version 7 form (a list of `@` and `&` layers, `_ &` for the tile's background) open as pattern swatches,
   with a fill's offset, scale, rotation, reflection and shear applied before its matrix.
   Its area type with several linked areas opens as threaded frames, one for each area with its own matrix,