Use the published Wallace threadcount, and scale the weave to the sett

Two separate faults. The pattern was wrong, and the scale was broken.

Pattern: the sett is published as K/4 R32 K32 Y/4, the slashes marking
pivots, which reflects out to K4 R32 K32 Y4 K32 R32 — 136 threads, about
half black and half red with a yellow line worth 3%. I had the structure
inverted: the yellow overstripe belongs down the centre of a wide black
band, and the narrow black guard belongs between two red blocks. Mine put
yellow between narrow blacks and the wide black elsewhere, which is why it
read as a generic check rather than as Wallace.

Scale: thread width was a fixed fraction of the screen while the sett grew
from 84 threads to 216, so a repeat became 933dp on a 360dp phone and only
0.39 of one was ever visible. The cloth had zoomed into a few enormous
blocks and stopped being a weave at all — that is the part that got worse,
not the colours. Thread width is now derived from the sett, so a couple of
full repeats are on screen whatever the threadcount says, and changing the
count rescales instead of silently magnifying.

The icon is generated from the same numbers at one repeat across the
adaptive safe zone.

Threadcount cross-checked against two independent sources rather than
guessed; recorded in Tartan.kt and the README so the next change starts
from the published figures.

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_015qjfMiPUDshdKEUa6vxqzN

README.md

@@ -70,14 +70,15 @@ drawable, so it stays sharp at every density and needs no PNGs.
 
 Two honest caveats:
 
-- **The sett is matched by eye, not to a registered threadcount.**
-  `WallaceSett` is written as a half-sett and reflected about its pivots, the way
-  a threadcount is published: gold 6, black 6, red 36, black 24, red 36, black 6.
-  That gives a red ground at about two thirds, black bands alternating wide and
-  narrow, and one thin gold overstripe per repeat flanked by black — matched
-  against a reference swatch rather than to the Scottish Register of Tartans.
-  Substituting registered counts is an edit to that one list; the icon is
-  generated from the same numbers, so both follow.
+- **The sett is the published threadcount: `K/4 R32 K32 Y/4`.** The slashes are
+  pivots, so `WallaceSett` holds the half-sett and reflects it out to
+  `K4 R32 K32 Y4 K32 R32` — 136 threads, about half black, half red, with a
+  yellow line worth 3%. Two details define the pattern and are easy to get
+  backwards: the yellow overstripe runs down the *centre of a wide black band*,
+  and the narrow black guard sits *between two red blocks*. The icon is
+  generated from the same numbers, so the icon and the splash cannot drift.
+  Weave scale is derived from the sett rather than fixed, so changing the
+  threadcount rescales both instead of silently zooming in.
 - **The typeface is bundled under a licence.** Uncial Antiqua, © 2011 Brian J.
   Bonislawsky DBA Astigmatic, Reserved Font Name "Uncial Antiqua", used under
   the SIL Open Font License 1.1. The full licence is at