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/packages/hermes-ink/src/ink/events/cmd-shortcuts.test.ts

@@ -39,6 +39,15 @@ describe('enhanced keyboard modifier parsing', () => {
     expect(event.key.super).toBe(true)
   })
 
+  it('preserves forwarded VS Code/Cursor Cmd+C copy sequence as ctrl+super+c', () => {
+    const parsed = parseOne('\u001b[99;13u')
+    const event = new InputEvent(parsed)
+
+    expect(parsed.name).toBe('c')
+    expect(event.key.ctrl).toBe(true)
+    expect(event.key.super).toBe(true)
+  })
+
   it('preserves Cmd on word-delete and word-navigation sequences', () => {
     const backspace = new InputEvent(parseOne('\u001b[127;9u'))
     const left = new InputEvent(parseOne('\u001b[1;9D'))