Universal-props gate: the planted token sample is assembled at runtime, not committed as a literal

The TOK-LITERAL self-test planted a string shaped like a real Mapbox token,
which is itself what the rule forbids and reads as a leaked credential to any
secret scan. The sample is now built at runtime from plainly fake parts
('example', 'not-a-token') in the same pk. + base64url + tail shape, so the
self-test still proves the rule fires, and no token-shaped literal is left in
the tree.

internal/check-universal-props.mjs

@@ -167,13 +167,18 @@ const run = (rule, src) => rule.test ? rule.test(src) : [...src.matchAll(rule.re
 const lineOf = (src, idx) => src.slice(0, idx).split('\n').length
 
 // ── self-test: every rule must see a planted violation ─────────────────────────────────────────
+// The TOK-LITERAL sample is ASSEMBLED HERE, never written as one literal: a committed string shaped like a
+// real Mapbox token is itself what that rule forbids, and reads as a leaked credential to any secret scan.
+// It is plainly fake ('example, not a token'), yet shaped like one: pk. + base64url JSON + . + a tail, which
+// is all the rule's regex looks for, so the self-test still proves the rule fires.
+const FAKE_TOKEN = 'pk.' + Buffer.from('{"u":"example","note":"not-a-token"}').toString('base64url') + '.' + 'x'.repeat(22)
 const PLANTED = `
   map.setStyle(isDark ? 'mapbox://styles/mapbox/dark-v11' : 'x')
   const m2 = new gl.Map({ container: el, style: 'mapbox://styles/mapbox/light-v11' })
   const p = new mapboxgl.Popup()
   useMapInstance({ container: el, provider: 'mapbox' })
   const tk = window.DOXA_TOKEN
-  const t = 'pk.eyJ1IjoiZXhhbXBsZSIsImEiOiJjbGFudGVkIn0'
+  const t = '${FAKE_TOKEN}'
   n.toLocaleString('en-US')
   const r = await fetch(base + '/api/people-groups/list?fields=slug')
   const dsm = new DataSourceManager({ locale: 'en' })