docs(readme): re-measure the selftest counts - 868 and 792 were both wrong

The public surface carried two different wrong sums for the same fact. The
badge said 868 (0.33.0's true total; 0.33.1 added 25 board checks without
re-summing) and the five `## Development` comments said 220/360/73/99/40 =
792, stale far longer. Neither matched the other, which is the tell.

Measured on b57a1ea by running all five suites under /bin/bash (3.2), not by
re-deriving from CHANGELOG: coord 257, board 393, route 73, orders 116,
state-line-guard 54 = 893, 0 failed in every summary. The comments keep what
they carry (what each suite covers); only the number moved.

grep for the old values across every *.md outside CHANGELOG: 5 hits before
(README:17,198,199,201,202), 0 after. CHANGELOG history is left as written -
it was true at the time - with an Unreleased entry recording the re-measure
and the commit it was taken against.

No code, no version bump, no tag.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -5,6 +5,21 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Fixed
+
+- **README's selftest numbers were re-measured, not re-derived.** The badge said
+  `selftest_checks-868` and the five `## Development` comments said
+  220/360/73/99/40 = 792 - two different wrong sums on the same public surface,
+  neither matching the other. The five suites were run under `/bin/bash` (3.2)
+  on `b57a1ea` and reported `coord 257`, `board 393`, `route 73`, `orders 116`,
+  `state-line-guard 54` = **893**, 0 failed in every summary. 0.33.0's entry
+  below records 257+368+73+116+54 = 868 and was true when written; 0.33.1 added
+  25 board checks (368 -> 393) without re-summing, and the comment block had been
+  stale far longer. No code, no version bump: the number furthest from the meter
+  rots first, and only the number moved.
+
 ## [0.33.0] - 2026-09-04
 
 ### Added