C4 fix - five undefined token names rendered surfaces transparent

The T9.9 token sweep pointed seven files (help.js, auth-guard.js, wp-format.js,
project-data.js, index.html, field.html, wp-creation-app.js) at Carbon names
the theme never defined: --cds-layer-01/-02, --cds-border-subtle-01/-strong-01,
--cds-layer-hover-01. theme-light.css carries no -01 suffixes. An undefined
var() invalidates the whole declaration, so the help-centre modal, the
change-password and language dialogs, the print popup's inlined values, the
creator nav drawer and the sync badge all rendered TRANSPARENT backgrounds -
reported by Nick against the help menu, 2026-08-20.

Renamed every consumer to the canonical tokens (--cds-layer, --cds-layer-accent,
--cds-layer-hover, --cds-border-subtle, --cds-border-strong), matched to the
hex each replacement originally stood in for. color_check gains check 3: every
var() consumed anywhere must resolve to a definition somewhere - the class of
this bug, pinned. Verified live: the modal computes rgb(255,255,255) over an
opaque gray nav, and the language dialog is opaque too. BL-025 logged for the
one wrong-base-colour rgba tint noticed in passing.

Item: C4 (regression in its own enforcement). Probe: color_check 5/5.

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

html/index.html

@@ -432,7 +432,7 @@
          never renders). Visually its own thing, so nobody opens one thinking
          it is live: the server refuses every write regardless. -->
     <section class="section" id="archived-projects" hidden
-             style="border:1px dashed var(--cds-border-subtle-01); background:var(--cds-layer-01); opacity:.92">
+             style="border:1px dashed var(--cds-border-subtle); background:var(--cds-layer-accent); opacity:.92">
       <h2>Archived projects</h2>
       <p style="font-size:13px; color:var(--cds-text-secondary)">Read-only. Visible to project
         admins only. Opening one lets you read everything; nothing on it can be changed while