Soften Fast mode plan usage copy (#18601)

Fast mode TUI copy currently names a specific plan-usage multiplier in
two lightweight promo/help surfaces. This swaps that exact multiplier
language for the broader increased plan usage wording we use elsewhere.

There are no behavior changes here; the slash command and startup tip
still point users at the same Fast mode flow.

codex-rs/tui/src/slash_command.rs

@@ -97,7 +97,9 @@ impl SlashCommand {
             SlashCommand::MemoryDrop => "DO NOT USE",
             SlashCommand::MemoryUpdate => "DO NOT USE",
             SlashCommand::Model => "choose what model and reasoning effort to use",
-            SlashCommand::Fast => "toggle Fast mode to enable fastest inference at 2X plan usage",
+            SlashCommand::Fast => {
+                "toggle Fast mode to enable fastest inference with increased plan usage"
+            }
             SlashCommand::Personality => "choose a communication style for Codex",
             SlashCommand::Realtime => "toggle realtime voice mode (experimental)",
             SlashCommand::Settings => "configure realtime microphone/speaker",

codex-rs/tui/src/tooltips.rs

@@ -10,7 +10,8 @@ const IS_MACOS: bool = cfg!(target_os = "macos");
 const IS_WINDOWS: bool = cfg!(target_os = "windows");
 
 const APP_TOOLTIP: &str = "Try the **Codex App**. Run 'codex app' or visit https://chatgpt.com/codex?app-landing-page=true";
-const FAST_TOOLTIP: &str = "*New* Use **/fast** to enable our fastest inference at 2X plan usage.";
+const FAST_TOOLTIP: &str =
+    "*New* Use **/fast** to enable our fastest inference with increased plan usage.";
 const OTHER_TOOLTIP: &str = "*New* Build faster with the **Codex App**. Run 'codex app' or visit https://chatgpt.com/codex?app-landing-page=true";
 const OTHER_TOOLTIP_NON_MAC: &str = "*New* Build faster with Codex.";
 const FREE_GO_TOOLTIP: &str =