feat(desktop): P17 村民走路节奏差异化（农夫/货郎/书生 纯 tick 节奏）

1 files changed, 46 insertions, 8 deletions

diff --git a/src/LivingVillage.Desktop/VillageArt.fs b/src/LivingVillage.Desktop/VillageArt.fs
index 489da23..11a6d71 100644
--- a/src/LivingVillage.Desktop/VillageArt.fs
+++ b/src/LivingVillage.Desktop/VillageArt.fs
@@ -79,6 +79,19 @@ module VillageArt =
         | GreyCap
         | StrawHat
 
+    /// Presentation-only occupational archetype. Kernel NPCs carry no occupation, so the
+    /// visible trade is a pure function of NpcId; three walking rhythms coexist on screen.
+    type NpcTrade =
+        | Farmer
+        | Peddler
+        | Scholar
+
+    /// Per-trade cadence in simulation ticks plus a phase offset, all deterministic.
+    type WalkRhythm =
+        { WalkWindow: int64
+          IdleWindow: int64
+          PhaseOffset: int64 }
+
     type FacingDirection =
         | NorthFacing
         | SouthFacing
@@ -291,23 +304,48 @@ module VillageArt =
         let remainder = value % divisor
         if remainder < 0L then remainder + divisor else remainder
 
-    /// Four-pose walk cycle over a 16-tick window (one pose per 4 sim ticks).
-    let animationFrame (tick: int64) : AnimationFrame =
-        match positiveModulo64 4L (tick / 4L) with
+    /// Trade cycle: NPCs repeat Farmer -> Peddler -> Scholar by id, so all three rhythms
+    /// are present without touching kernel state.
+    let npcTrade (NpcId npcId) : NpcTrade =
+        match positiveModulo 3 npcId with
+        | 0 -> Farmer
+        | 1 -> Peddler
+        | _ -> Scholar
+
+    /// Farmer ambles at the original cadence; Peddler shuffles faster; Scholar strolls slower.
+    let rhythmFor (trade: NpcTrade) : WalkRhythm =
+        match trade with
+        | Farmer -> { WalkWindow = 4L; IdleWindow = 24L; PhaseOffset = 0L }
+        | Peddler -> { WalkWindow = 3L; IdleWindow = 20L; PhaseOffset = 1L }
+        | Scholar -> { WalkWindow = 6L; IdleWindow = 36L; PhaseOffset = 2L }
+
+    /// Four-pose walk cycle at a rhythm's window (one pose per WalkWindow sim ticks).
+    let animationFrameFor (rhythm: WalkRhythm) (tick: int64) : AnimationFrame =
+        match positiveModulo64 4L (tick / rhythm.WalkWindow + rhythm.PhaseOffset) with
         | 0L -> FrameOne
         | 1L -> FrameTwo
         | 2L -> FrameThree
         | _ -> FrameFour
 
-    /// Two-pose standing breath cycle over a slower 48-tick window, fully deterministic.
-    let idleFrame (tick: int64) : IdleFrame =
-        match positiveModulo64 2L (tick / 24L) with
+    /// Two-pose standing breath cycle at a rhythm's IdleWindow, fully deterministic.
+    let idleFrameFor (rhythm: WalkRhythm) (tick: int64) : IdleFrame =
+        match positiveModulo64 2L (tick / rhythm.IdleWindow + rhythm.PhaseOffset) with
         | 0L -> IdleOne
         | _ -> IdleTwo
 
     /// Picks the walk cycle while moving and the breath cycle while standing still.
+    let characterFrameFor (rhythm: WalkRhythm) (isMoving: bool) (tick: int64) : CharacterFrame =
+        if isMoving then WalkFrame(animationFrameFor rhythm tick) else IdleFrame(idleFrameFor rhythm tick)
+
+    /// Farmer cadence is the base cadence (window 4/24, phase 0), preserving older semantics.
+    let animationFrame (tick: int64) : AnimationFrame =
+        animationFrameFor (rhythmFor Farmer) tick
+
+    let idleFrame (tick: int64) : IdleFrame =
+        idleFrameFor (rhythmFor Farmer) tick
+
     let characterFrame (isMoving: bool) (tick: int64) : CharacterFrame =
-        if isMoving then WalkFrame(animationFrame tick) else IdleFrame(idleFrame tick)
+        characterFrameFor (rhythmFor Farmer) isMoving tick
 
     /// Water surface ripple phase: three frames, one per 32 simulation ticks, fully deterministic.
     let waterFrameTick (tick: int64) : int =
@@ -342,7 +380,7 @@ module VillageArt =
     let npcSpriteSpec (npcId: NpcId) (direction: FacingDirection) (isMoving: bool) (tick: int64) : NpcSpriteSpec =
         { Variant = npcVisualVariant npcId
           Direction = direction
-          Frame = characterFrame isMoving tick }
+          Frame = characterFrameFor (rhythmFor (npcTrade npcId)) isMoving tick }
 
     /// Villagers breathe while standing at their target and walk while approaching it.
     let npcSpriteSpecAtTarget (npcId: NpcId) (position: Vec2) (target: Vec2) (tick: int64) : NpcSpriteSpec =