fix(tui): restore macOS copy behavior and theme polish (#17131)

This PR groups the TUI fixes that restore macOS Terminal usability and clean up the theme/composer regressions:

- copy transcript selections on macOS drag-release so Terminal.app users can copy while mouse tracking is enabled
- copy composer selections on macOS drag-release; composer selection is internal to TextInput and does not use the global Ink selection bus
- keep IDE Cmd+C forwarding setup macOS-only, and make keybinding conflict checks respect simple when-clause overlap/negation
- force truecolor before chalk initializes (unless NO_COLOR / FORCE_COLOR / HERMES_TUI_TRUECOLOR opt-outs apply) so the default banner keeps its gold/amber/bronze gradient in Terminal.app
- move TUI surfaces onto semantic theme tokens and preserve skin prompt symbols as bare tokens with renderer-owned spacing
- render focused placeholders as dim hint text in TTY mode instead of inverse/selected-looking synthetic cursor text

ui-tui/src/components/queuedMessages.tsx

@@ -23,14 +23,14 @@ export function QueuedMessages({ cols, queueEditIdx, queued, t }: QueuedMessages
 
   return (
     <Box flexDirection="column" marginTop={1}>
-      <Text color={t.color.dim} dimColor>
+      <Text color={t.color.muted} dimColor>
         {`queued (${queued.length})${
           queueEditIdx !== null ? ` · editing ${queueEditIdx + 1} · Ctrl+X delete · Esc cancel` : ''
         }`}
       </Text>
 
       {q.showLead && (
-        <Text color={t.color.dim} dimColor>
+        <Text color={t.color.muted} dimColor>
           {' '}
           …
         </Text>
@@ -41,14 +41,14 @@ export function QueuedMessages({ cols, queueEditIdx, queued, t }: QueuedMessages
         const active = queueEditIdx === idx
 
         return (
-          <Text color={active ? t.color.amber : t.color.dim} dimColor key={`${idx}-${item.slice(0, 16)}`}>
+          <Text color={active ? t.color.accent : t.color.muted} dimColor key={`${idx}-${item.slice(0, 16)}`}>
             {active ? '▸' : ' '} {idx + 1}. {compactPreview(item, Math.max(16, cols - 10))}
           </Text>
         )
       })}
 
       {q.showTail && (
-        <Text color={t.color.dim} dimColor>
+        <Text color={t.color.muted} dimColor>
           {'  '}…and {queued.length - q.end} more
         </Text>
       )}