feat(m6b): add playable menu and save flow

[Change Nature]
- This commit adds the M6b desktop menu and persistence integration.

[New Capability]
- Provide new game, continue, settings, controls, load error, save, load, and exit flows.
- Provide a bounded autoplay flow covering menu navigation and persistence.

[Implementation]
- Add pure menu state transitions and focused M6b coverage.
- Connect menu commands to simulation controls, WorldSave, view resets, and rendering.

[Impact]
- Desktop runtime gains the playable M6b front end without changing out-of-scope files.
- Release focused and solution test suites remain passing.

1 files changed, 192 insertions, 0 deletions

diff --git a/src/LivingVillage.Desktop/MenuState.fs b/src/LivingVillage.Desktop/MenuState.fs
new file mode 100644
index 0000000..78d846c
--- /dev/null
+++ b/src/LivingVillage.Desktop/MenuState.fs
@@ -0,0 +1,192 @@
+namespace LivingVillage.Desktop
+
+open LivingVillage.Kernel
+
+type MenuPage =
+    | MainMenu
+    | Settings
+    | Controls
+    | Playing
+    | LoadError
+
+type MenuItem =
+    | ContinueItem
+    | NewGameItem
+    | LoadItem
+    | SettingsItem
+    | ControlsItem
+    | ExitItem
+
+type MenuSetting =
+    | OneXSetting
+    | TwoXSetting
+    | FiveXSetting
+    | PauseSetting
+
+type MenuInput =
+    | Up
+    | Down
+    | Confirm
+    | Back
+
+type MenuCommand =
+    | NoCommand
+    | ContinueGame
+    | StartNewGame
+    | LoadGame
+    | ApplySettings of SimulationControl
+    | ExitGame
+
+type ControlRow =
+    { Keys: string
+      Action: string }
+
+type MenuState =
+    { Page: MenuPage
+      Selected: int
+      HasCurrentWorld: bool
+      ReturnPage: MenuPage
+      Settings: SimulationControl
+      Error: string option }
+
+module MenuState =
+
+    let settings : MenuSetting list =
+        [ OneXSetting; TwoXSetting; FiveXSetting; PauseSetting ]
+
+    let controlRows : ControlRow list =
+        [ { Keys = "WASD"; Action = "MOVE" }
+          { Keys = "E"; Action = "INTERACT" }
+          { Keys = "1-6"; Action = "DIALOGUE" }
+          { Keys = "Q"; Action = "OBSERVE" }
+          { Keys = "TAB"; Action = "NEEDS" }
+          { Keys = "C"; Action = "CHRONICLE" }
+          { Keys = "L"; Action = "RELATIONS" }
+          { Keys = "P"; Action = "PAUSE" }
+          { Keys = "F1/F2/F3"; Action = "SPEED" }
+          { Keys = "F6"; Action = "SAVE" }
+          { Keys = "F7"; Action = "LOAD" }
+          { Keys = "ESC"; Action = "MENU OR CLOSE" }
+          { Keys = "UP/DOWN"; Action = "SELECT" }
+          { Keys = "ENTER"; Action = "CONFIRM" } ]
+
+    let create (simulationControl: SimulationControl) (hasCurrentWorld: bool) : MenuState =
+        { Page = MainMenu
+          Selected = 0
+          HasCurrentWorld = hasCurrentWorld
+          ReturnPage = MainMenu
+          Settings = simulationControl
+          Error = None }
+
+    let items (state: MenuState) : MenuItem list =
+        if state.HasCurrentWorld then
+            [ ContinueItem; NewGameItem; LoadItem; SettingsItem; ControlsItem; ExitItem ]
+        else
+            [ NewGameItem; LoadItem; SettingsItem; ControlsItem; ExitItem ]
+
+    let settingsLabel setting : string =
+        match setting with
+        | OneXSetting -> "1X"
+        | TwoXSetting -> "2X"
+        | FiveXSetting -> "5X"
+        | PauseSetting -> "PAUSE"
+
+    let itemLabel item : string =
+        match item with
+        | ContinueItem -> "CONTINUE"
+        | NewGameItem -> "NEW GAME"
+        | LoadItem -> "LOAD SAVE"
+        | SettingsItem -> "SETTINGS"
+        | ControlsItem -> "CONTROLS"
+        | ExitItem -> "QUIT"
+
+    let private optionsFor (state: MenuState) : int =
+        match state.Page with
+        | MainMenu -> items state |> List.length
+        | Settings -> settings.Length
+        | _ -> 0
+
+    let private moveBy (delta: int) (state: MenuState) : MenuState =
+        let count = optionsFor state
+        if count = 0 then
+            state
+        else
+            let next = (state.Selected + delta) % count
+            let wrapped = if next < 0 then next + count else next
+            { state with Selected = wrapped }
+
+    let move direction state =
+        match direction with
+        | Up -> moveBy -1 state
+        | Down -> moveBy 1 state
+        | Confirm
+        | Back -> state
+
+    let selectedItem (state: MenuState) : MenuItem =
+        items state |> List.item state.Selected
+
+    let selectedSetting (state: MenuState) : MenuSetting =
+        settings |> List.item state.Selected
+
+    let private selectedControl (state: MenuState) : SimulationControl =
+        match selectedSetting state with
+        | OneXSetting -> { state.Settings with Paused = false; Speed = OneX }
+        | TwoXSetting -> { state.Settings with Paused = false; Speed = TwoX }
+        | FiveXSetting -> { state.Settings with Paused = false; Speed = FiveX }
+        | PauseSetting -> { state.Settings with Paused = true }
+
+    let enterGame (state: MenuState) : MenuState =
+        { state with Page = Playing; Selected = 0; ReturnPage = MainMenu; Error = None }
+
+    let setCurrentWorld (hasCurrentWorld: bool) (state: MenuState) : MenuState =
+        { state with HasCurrentWorld = hasCurrentWorld }
+
+    let setSettings (simulationControl: SimulationControl) (state: MenuState) : MenuState =
+        { state with Settings = simulationControl }
+
+    let openMain (state: MenuState) : MenuState =
+        { state with Page = MainMenu; Selected = 0; ReturnPage = MainMenu; Error = None }
+
+    let openSettings (state: MenuState) : MenuState =
+        { state with Page = Settings; Selected = 0; ReturnPage = state.Page; Error = None }
+
+    let openControls (state: MenuState) : MenuState =
+        { state with Page = Controls; Selected = 0; ReturnPage = state.Page; Error = None }
+
+    let showLoadError (message: string) (state: MenuState) : MenuState =
+        { state with Page = LoadError; Selected = 0; ReturnPage = MainMenu; Error = Some message }
+
+    let private returnFromSubpage (state: MenuState) : MenuState =
+        match state.ReturnPage with
+        | Playing -> { state with Page = Playing; Selected = 0; Error = None }
+        | _ -> openMain state
+
+    let private confirmMain (state: MenuState) : MenuState * MenuCommand =
+        match selectedItem state with
+        | ContinueItem -> enterGame state, ContinueGame
+        | NewGameItem -> state, StartNewGame
+        | LoadItem -> state, LoadGame
+        | SettingsItem -> openSettings state, NoCommand
+        | ControlsItem -> openControls state, NoCommand
+        | ExitItem -> state, ExitGame
+
+    let update (input: MenuInput) (state: MenuState) : MenuState * MenuCommand =
+        match input with
+        | Up -> move Up state, NoCommand
+        | Down -> move Down state, NoCommand
+        | Back ->
+            match state.Page with
+            | MainMenu -> state, ExitGame
+            | Settings
+            | Controls -> returnFromSubpage state, NoCommand
+            | LoadError -> openMain state, NoCommand
+            | Playing -> openMain state, NoCommand
+        | Confirm ->
+            match state.Page with
+            | MainMenu -> confirmMain state
+            | Settings ->
+                let nextSettings = selectedControl state
+                { state with Settings = nextSettings }, ApplySettings nextSettings
+            | Controls -> state, NoCommand
+            | LoadError -> openMain state, NoCommand
+            | Playing -> state, NoCommand