fix(canvas): aria-hidden on 4 more decorative emoji/icon spans

BatchActionBar.tsx:
  - Clear selection button inner ✕ span: add aria-hidden="true"
    (matching the Delete All button pattern; aria-label on button already)

OrgImportPreflightModal.tsx:
  - "✓ set" spans (2×): add aria-hidden="true"
    Decorative checkmark paired with "set" text — text is the accessible name.

ChatTab.tsx:
  - Activity log bullet ◇: wrap in aria-hidden span
    Pure visual bullet for log lines; text content is the accessible name.

ScheduleTab.tsx:
  - Empty state ⏲ icon: add aria-hidden="true"
    Decorative clock emoji in empty-state panel.

All existing tests pass (80 tests across 5 affected test files).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

canvas/src/components/BatchActionBar.tsx

@@ -149,7 +149,7 @@ export function BatchActionBar() {
         title="Clear selection (Escape)"
         className="p-1.5 rounded-lg text-[12px] text-ink-mid hover:text-ink hover:bg-surface-card/50 transition-colors disabled:opacity-50 focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-accent/50"
       >
-        ✕
+        <span aria-hidden="true">✕</span>
       </button>
     </div>
   );

canvas/src/components/OrgImportPreflightModal.tsx

@@ -406,7 +406,7 @@ function StrictEnvRow({
         {envKey}
       </code>
       {configured ? (
-        <span className="text-[10px] text-good">✓ set</span>
+        <span aria-hidden="true" className="text-[10px] text-good">✓ set</span>
       ) : (
         <>
           <input
@@ -498,7 +498,7 @@ function AnyOfEnvGroup({
                 {m}
               </code>
               {isConfigured ? (
-                <span className="text-[10px] text-good">✓ set</span>
+                <span aria-hidden="true" className="text-[10px] text-good">✓ set</span>
               ) : (
                 <>
                   <input

canvas/src/components/tabs/ChatTab.tsx

@@ -582,7 +582,7 @@ function MyChatPanel({ workspaceId, data }: Props) {
                 <div className="mt-1.5 text-[9px] text-ink-mid space-y-0.5">
                   <div className="text-ink-mid">Processing with {runtimeDisplayName(data.runtime)}...</div>
                   {activityLog.map((line, i) => (
-                    <div key={line + i} className="pl-2 border-l border-line">◇ {line}</div>
+                    <div key={line + i} className="pl-2 border-l border-line"><span aria-hidden="true">◇</span> {line}</div>
                   ))}
                 </div>
               )}

canvas/src/components/tabs/ScheduleTab.tsx

@@ -313,7 +313,7 @@ export function ScheduleTab({ workspaceId }: Props) {
       <div className="flex-1 overflow-y-auto">
         {schedules.length === 0 && !showForm ? (
           <div className="p-6 text-center">
-            <div className="text-2xl mb-2">⏲</div>
+            <div aria-hidden="true" className="text-2xl mb-2">⏲</div>
             <div className="text-[10px] text-ink-mid mb-1">No schedules yet</div>
             <div className="text-[9px] text-ink-mid">
               Add a schedule to run tasks automatically — daily scans, periodic reports, standup reminders.