docs: turn the accepted panel design into an enforceable contract

panel-redesign.md is rewritten for the accepted direction: three layers
(Bulma as shipped, adapters, own sp- components), the page layouts, what
an implementer must not do, and how that is enforced — guard tests that
land before any template, a design-first CI step, and acceptance by
evidence (test output plus a screenshot of every page beside its mockup,
reviewed by a model that did not write the step).

A components page shows every building block in every state; a screen
may be built from nothing else. panel/check.py lints the mockups against
the contract (class vocabulary, CSS bans on !important, id and page
selectors and stray widths, page structure) and writes
panel/outlines.json, the per-screen component skeleton an implementation
is compared with, so a different design cannot pass as this one.

Own modifier classes now carry the sp- prefix (sp-warn, sp-fail, sp-big,
sp-danger-zone, ...) so the vocabulary is machine-checkable; the lint
also caught a width set outside the layout in the mockup's own CSS.

Agent rule .cursor/rules/panel-design.mdc; roadmap row and section
updated (0/15, still candidate).

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

docs/assets/panel-redesign/panel/in-domain-delete.html

@@ -71,7 +71,7 @@
 
     <div class="columns">
       <div class="column is-7">
-        <div class="box is-danger-zone">
+        <div class="box sp-danger-zone">
           <div class="sp-box-head"><span class="sp-no"><i class="ti ti-alert-triangle"></i></span><h2>This cannot be undone</h2></div>
           <div class="sp-box-body">
             <p class="mb-3">Deleting the inbound domain <strong>lists.example.org</strong> will:</p>