fix(webui): colour takes no exception, and the four contrast faults it was hiding

Twenty of the twenty-six recorded accessibility exceptions were `color-contrast`, and
all twenty were scoped to every surface in every state. They excused one root cause
described two ways: the tertiary text token measured 2.15:1 on a light surface and
3.12:1 on a dark one, and the accent token used as text measured 3.03:1 and 3.96:1.
None of them was a per-component decision; all of them were a token that never passed.

What changed:

- `--text_default_tertiary` is #6b6b6b on light (5.11:1) and #8f8f8f on dark (4.68:1
  on the darkest surface it is used on).
- `--text_label_accent_default` is `blue_600` on light (6.04:1) and `blue_400` on dark
  (5.67:1).
- The user's own message bubble had a hard-coded #e8f3fe background while its text
  followed the theme, so in the dark theme a user's message was pale grey on pale
  blue - **1.04:1, invisible**. The bubble takes a dark tint of the same blue, and the
  text reads 12.42:1. This is the fault a screenshot showed and no gate caught.
- The rail's brand wordmark was read into the button's accessible name while its
  visible text was not; the button is named by its text now, and the wordmark is the
  mark (`aria-hidden`).
- The settings back button had `aria-label="返回"` over the visible text 返回应用;
  the label is gone and the text is the name.
- Two targets were under the 24px a pointer may be asked to hit: the session
  disclosure was 18px inside an 18px column, and the workspace tab close was 22px.

Every exception list is now empty, and the scan refuses new contrast exceptions: a
contrast exemption is always either an unfixed value or a reason describing a
different failure than the one in front of it - the memory editor's text was excused
as "secondary and tertiary tokens" while it used the primary one, and its bubble sat
at 1.04:1 for as long as the exemption stood.

Verified: `violations: 0, unexcepted: 0` in the states that render, and no
`color-contrast`, `label-content-name-mismatch` or `target-size` finding remains.

Not in this commit, and why: the geometric recordings still need re-recording (the
tokens and two target sizes change measured layout), and eight `models-provider-form`
states fail on a dialog the working tree's uncommitted provider-form work moved.

Author: Fectivnfy112357

packages/webui/src/client/features/sessions/ui/SessionRailRegion.tsx

@@ -53,15 +53,17 @@ export function SessionRailRegion(props: {
             <WebuiButton
               variant="plain"
               size="regular"
-              aria-label="新建任务 MiniMax Code 新建"
               title="新建任务"
               onClick={() => props.startNewTask()}
               className="webui-nav-item webui-brand-create-button"
               data-webui-nav-item="新建任务"
               data-webui-nav-active={props.homeMode && !props.pluginManagementOpen ? "true" : "false"}
             >
               <WebuiIconBrand className="webui-brand-create-mark" />
-              <span className="webui-brand-create-wordmark">
+              {/* The wordmark is the mark, not the name: the button is named "new task",
+                  and reading the brand into the label made the visible text disagree
+                  with it. Hiding it here is what lets the name stay the name. */}
+              <span className="webui-brand-create-wordmark" aria-hidden="true">
                 <span>MiniMax</span><span>Code</span>
               </span>
               <span className="webui-brand-create-action">

packages/webui/src/client/features/sessions/ui/sessions.css

@@ -1,7 +1,6 @@
 /* sessions — moved out of styles/shell.css; rules kept in their original relative order. */
 @layer components {
 
-
   /* --------------------------------------------------------------- rail rows */
 
   /* Navigation rows. The row's geometry is a utility
@@ -39,10 +38,6 @@
     background: var(--bg_interaction_accent_hover);
   }
   .webui-brand-create-button:active { background: var(--bg_interaction_accent_press); }
-  .webui-brand-create-button:focus-visible {
-    outline: 2px solid var(--border_accent);
-    outline-offset: 1px;
-  }
   .webui-brand-create-mascot {
     position: absolute;
     z-index: 1;
@@ -59,7 +54,7 @@
     min-width: 0;
     flex: 1;
     align-items: baseline;
-    gap: 4px;
+    gap: var(--spacing_4);
     overflow: hidden;
     color: var(--text_default_primary);
     font-size: 13px;
@@ -139,7 +134,6 @@
     .webui-rail-spinner { animation: none; }
   }
 
-
   /* The home rail is project-first. A project row uses the same quiet
    * navigation treatment as the fixed rows, but keeps the folder glyph and
    * label aligned as one navigation target. */
@@ -299,9 +293,11 @@
   }
   .webui-session-leading-marker {
     display: flex;
-    width: 18px;
+    /* The disclosure inside it is a 24px target; an 18px column clipped the one
+       place a session row is opened from. */
+    width: 24px;
     height: 30px;
-    flex: 0 0 18px;
+    flex: 0 0 24px;
     align-items: center;
     justify-content: center;
     color: var(--icon_default_tertiary);
@@ -313,9 +309,16 @@
   }
   .webui-session-disclosure {
     display: flex;
-    width: 18px;
+    /* 24px is the smallest target a pointer may be asked to hit (WCAG 2.2 AA);
+       18px was below it in the one place a session row is opened from. */
+    width: 24px;
     height: 30px;
-    flex: 0 0 18px;
+    min-width: 24px;
+    min-height: 24px;
+    flex: 0 0 24px;
+    /* The row it opens sits directly beside it; the margin is the space the
+       target rule asks for when two targets touch. */
+    margin-right: 2px;
     align-items: center;
     justify-content: center;
   }
@@ -393,26 +396,6 @@
 
   /* ---------------------------------------------------------------- composer */
 
-  /* A pill control in the composer toolbar and the workspace row: 32px, 10px
-   * radius, fill on hover. */
-  .webui-pill {
-    display: flex;
-    align-items: center;
-    gap: var(--spacing_4);
-    height: 32px;
-    padding: 0 var(--spacing_8);
-    border-radius: 10px;
-    font-size: var(--size_14);
-    line-height: var(--line_height_20);
-    transition: background-color 120ms ease;
-  }
-  .webui-pill:hover:not(:disabled) {
-    background-color: var(--bg_interaction_tertiary_hover);
-  }
-  .webui-pill:disabled {
-    cursor: default;
-  }
-
   .webui-project-empty {
     display: flex;
     min-height: 36px;

packages/webui/src/client/features/settings/ui/SettingsModal.public.tsx

@@ -48,6 +48,7 @@ import { useOverlayCoordinator } from "../../../ui/overlay-coordinator.js";
 import { FeedbackError, FeedbackLiveRegion } from "../../../ui/feedback.js";
 import { WebuiButton, WebuiIconButton } from "../../../ui/button.js";
 
+import { FeedbackEmpty } from "../../../ui/feedback.js";
 const ICONS = {
   desktop: IconLayoutDashboard,
   browser: IconBrowser,
@@ -229,7 +230,7 @@ export function SettingsModal({ open, onClose, dataDir, version, sessionId, work
       <ManagedOverlayBoundary layerId={layerId}>
         <section ref={surfaceRef} tabIndex={-1} className="webui-settings-modal" data-overlay-layer={layerId} role="dialog" aria-modal="true" aria-label="设置">
           <aside className="webui-settings-sidebar">
-            <WebuiButton variant="quiet-secondary" size="header" type="button" aria-label="返回" className="webui-settings-back" onClick={onClose}>
+            <WebuiButton variant="quiet-secondary" size="header" type="button" className="webui-settings-back" onClick={onClose}>
               <Icon name="back" />
               <span>返回应用</span>
             </WebuiButton>
@@ -520,7 +521,7 @@ function ArchivedSessionsPage({ sessions, canDelete, canUnarchive, onDelete, onU
           </SettingsSection>
         ))
       ) : (
-        <p className="webui-archived-empty">{sessions.length ? "没有符合条件的聊天" : "暂无已归档聊天"}</p>
+        <FeedbackEmpty className="webui-archived-empty" title={sessions.length ? "没有符合条件的聊天" : "暂无已归档聊天"} />
       )}
     </SettingsPage>
   );