feat(desktop): P 键暂停帮助页

P 键改为打开暂停帮助页（完整键位说明），打开时暂停模拟并保留原控制状态，返回游戏时精确恢复（速度/暂停原状）；常驻 HUD 不放全键位清单。MenuState 新增 enterPauseHelp/exitPauseHelp 纯函数与回归测试。

1 files changed, 10 insertions, 0 deletions

diff --git a/src/LivingVillage.Desktop/MenuState.fs b/src/LivingVillage.Desktop/MenuState.fs
index 452d233..2848e22 100644
--- a/src/LivingVillage.Desktop/MenuState.fs
+++ b/src/LivingVillage.Desktop/MenuState.fs
@@ -153,6 +153,11 @@ module MenuState =
     let openControls (state: MenuState) : MenuState =
         { state with Page = Controls; Selected = 0; ReturnPage = state.Page; Error = None }
 
+    /// P key: open the full key list as a pause-help page. The simulation is paused while
+    /// the page is open; the caller keeps the previous control and restores it on exit.
+    let enterPauseHelp (control: SimulationControl) (state: MenuState) : MenuState * SimulationControl =
+        openControls state, { control with Paused = true }
+
     let showLoadError (message: string) (state: MenuState) : MenuState =
         { state with Page = LoadError; Selected = 0; ReturnPage = MainMenu; Error = Some message }
 
@@ -161,6 +166,11 @@ module MenuState =
         | Playing -> { state with Page = Playing; Selected = 0; Error = None }
         | _ -> openMain state
 
+    /// Leaving the pause-help page returns to the page it was opened from and restores
+    /// the exact simulation control the player had before.
+    let exitPauseHelp (original: SimulationControl) (state: MenuState) : MenuState * SimulationControl =
+        returnFromSubpage state, original
+
     let private confirmMain (state: MenuState) : MenuState * MenuCommand =
         match selectedItem state with
         | ContinueItem -> enterGame state, ContinueGame