feat(gates): WP-02 — harden check:tokens to whole-app colour guard

- Move the guard to scripts/check-tokens.sh; regex now catches hex +
  rgb()/hsl() (was hex-only) across ALL src/app components (was three
  ui/layout dirs). `token-ok` marker suppresses justified false positives;
  px stays out of scope (documented in the script).
- Zero exclusions: debug-state's dark code-editor palette moves to
  --app-devpanel-* tokens in styles.scss (the one exempt file), dropping its
  --exclude hole.
- Tokenize remaining hits: site-footer border via color-mix; three brief
  border widths via --rhc-border-width-* (new --rhc-border-width-lg: 3px).

Verified: planted violation fails the guard; GREEN + test-storybook:ci.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/app/brief/ui/letter-block/letter-block.component.ts

@@ -11,7 +11,7 @@ import { LetterBlock } from '@brief/domain/brief';
   imports: [RichTextEditorComponent, ButtonComponent],
   styles: [`
     :host{display:block}
-    .block{border-inline-start:3px solid var(--rhc-color-border-subtle);padding-inline-start:var(--rhc-space-max-md)}
+    .block{border-inline-start:var(--rhc-border-width-lg) solid var(--rhc-color-border-subtle);padding-inline-start:var(--rhc-space-max-md)}
     .meta{display:flex;justify-content:space-between;align-items:center;gap:var(--rhc-space-max-md);margin-block-end:var(--rhc-space-max-sm)}
     .controls{display:flex;gap:var(--rhc-space-max-sm)}
   `],