retire the last light-theme branches and fix three latent color bugs

Dark is now the only theme, so every `.dark` selector matched
unconditionally while each non-dark branch was unreachable. That left
fourteen `.dark &` blocks sitting on top of token-based base rules and
silently overriding them with hardcoded grays from the previous palette
(#333333, #999999, #cccccc, #f2f2f2, #1f1f1f, #2a2a2a). Merged each value
down into its base rule and deleted the wrapper, then replaced fifteen
more legacy grays with the CYBER tokens.

Three bugs surfaced along the way:

- FileEditor read `documentElement.classList.contains('dark')`, but the
  `dark` class is bound on `.app-root`, so Monaco always loaded the
  light `vs` theme inside the dark editor surface.
- CodexLoginModal, CopilotLoginModal and NousLoginModal wrote
  `border-color: var(--arcoblue-6, #165dff)` and VoiceApiFormModal wrote
  `color: var(--primary-6, #18a058)`. Those Arco variables hold bare
  RGB triplets, not colors, so each declaration was invalid and
  discarded — the hover border and link color stayed stock Arco
  blue/green instead of the cyan accent.
- JourneyView drew the pinned-node ring in amber, a leftover from the
  old palette.

Rendering-layer only: no store logic, no /chat-run payload, no message
rendering path.

packages/client/src/components/hermes/models/NousLoginModal.vue

@@ -201,14 +201,14 @@ startLogin()
   align-items: center;
   gap: 12px;
   padding: 12px 20px;
-  border: 1px solid var(--color-border-2, #e0e0e6);
+  border: 1px solid var(--border-color);
   border-radius: 8px;
   cursor: pointer;
   transition: border-color 0.2s;
-  background: var(--color-fill-2, #fafafa);
+  background: var(--bg-card);
 
   &:hover {
-    border-color: var(--arcoblue-6, #165dff);
+    border-color: var(--accent-primary);
   }
 }