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

website/docs/user-guide/features/skins.md

@@ -95,7 +95,7 @@ Text strings used throughout the CLI interface.
 | `welcome` | Welcome message shown at CLI startup | `Welcome to Hermes Agent! Type your message or /help for commands.` |
 | `goodbye` | Message shown on exit | `Goodbye! ⚕` |
 | `response_label` | Label on the response box header | ` ⚕ Hermes ` |
-| `prompt_symbol` | Symbol before the user input prompt | `❯ ` |
+| `prompt_symbol` | Symbol before the user input prompt (bare token, renderers add a trailing space) | `❯` |
 | `help_header` | Header text for the `/help` command output | `(^_^)? Available Commands` |
 
 ### Other top-level keys
@@ -167,7 +167,7 @@ branding:
   welcome: "Welcome to My Agent! Type your message or /help for commands."
   goodbye: "See you later! ⚡"
   response_label: " ⚡ My Agent "
-  prompt_symbol: "⚡ ❯ "
+  prompt_symbol: "⚡"
   help_header: "(⚡) Available Commands"
 
 tool_prefix: "┊"