Add configuration support for TUI input presets (#54379)

## What changed

Add `tui.presets` entries keyed by a single digit from `0` to `9`, each with an `input` prompt or slash command and an optional `label`. Expose presets in the configuration schema, load them into runtime configuration, and preserve them in TUI local settings.

Reject invalid slots, blank inputs, shell commands beginning with `!` after leading whitespace, and inputs exceeding 8,000 UTF-8 bytes.

## Testing

Extend the runtime configuration test to verify loading both a slash command with a label and a prompt without one.

GitOrigin-RevId: d2911e540bc50f05b4a5224abf17ce4ef5a18ea3

codex-rs/tui/src/local_settings.rs

@@ -84,6 +84,7 @@ impl LocalSettings {
                 agents_overview_grouping: config.tui_agents_overview_grouping,
                 resume_cwd: config.tui_resume_cwd,
                 keymap: config.tui_keymap.clone(),
+                quick_dials: config.tui_quick_dials.clone(),
                 model_availability_nux: config.model_availability_nux.clone(),
                 terminal_resize_reflow_max_rows: match config.terminal_resize_reflow.max_rows {
                     TerminalResizeReflowMaxRows::Auto => None,