feat(occupation): 职业系统第一片 — Kernel 结构 / bootstrap 注入 / 存档 v3

Occupation.fs（Kind/Profile/State + 农夫/渔夫/货郎/书生 中文名常量，按设计 §1 表给初始 Money/Energy/Inventory）；ItemKind 扩出 Fish/Spice/Scroll（basePrice 分支补齐，Food 10.0f 数值路径不变 → 无职业 digest 不动）；WorldBootstrap.initialWorldWithOccupation 默认 None = 旧行为（Money/Energy 覆盖，库存字段先留数据侧、物理挂接留交易单——取舍见 design §2-C 反对加字段）；WorldSave: v3 头仅在有职业时写入（保存 saveToFileWith / loadFromFileWith，v1/v2/v3 无职业类型默认，token 顺序 version|w|h|kind|task|story|…），默认路径 save 输出逐字节等同现行 v2；P10 测试 5 例（§1 表值、v3 round-trip、v1/v2 不吞档、双 seed 逐字节、中文名）；Kernel.Tests 引用 Desktop 以驱动 WorldBootstrap（取舍：不做测试专用 shim）。TaskToken/StoryStage 为 v3 占位（任务系统后续单实现）。

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diff --git a/src/LivingVillage.Kernel/Occupation.fs b/src/LivingVillage.Kernel/Occupation.fs
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+namespace LivingVillage.Kernel
+
+/// Occupation system first slice (design §1/§2, docs/design/occupation-system-design.md).
+/// Data lives beside the player only — NPCs are never occupied.
+/// Nothing here runs inside Sim.step; WorldBootstrap stamps the profile onto the
+/// world's avatar at creation time, which keeps the numeric state path untouched.
+module Occupation =
+
+    type Kind =
+        | Farmer
+        | Fisher
+        | Peddler
+        | Scholar
+
+    /// Chinese labels, shared for a later UI slice (农夫 / 渔夫 / 货郎 / 书生).
+    let nameOf (kind: Kind) : string =
+        match kind with
+        | Farmer -> "农夫"
+        | Fisher -> "渔夫"
+        | Peddler -> "货郎"
+        | Scholar -> "书生"
+
+    let saveToken (kind: Kind) : string =
+        match kind with
+        | Farmer -> "farmer"
+        | Fisher -> "fisher"
+        | Peddler -> "peddler"
+        | Scholar -> "scholar"
+
+    let all : Kind list = [ Farmer; Fisher; Peddler; Scholar ]
+
+    type Profile =
+        { Kind: Kind
+          InitialMoney: int
+          InitialEnergy: float32
+          InitialInventory: (Sim.ItemKind * int) list }
+
+    /// Initial values straight from the approved design §1 table.
+    let profileOf (kind: Kind) : Profile =
+        match kind with
+        | Farmer -> { Kind = Farmer; InitialMoney = 60; InitialEnergy = 100.0f; InitialInventory = [ Sim.Food, 12 ] }
+        | Fisher -> { Kind = Fisher; InitialMoney = 45; InitialEnergy = 95.0f; InitialInventory = [ Sim.Food, 8; Sim.Fish, 3 ] }
+        | Peddler -> { Kind = Peddler; InitialMoney = 90; InitialEnergy = 100.0f; InitialInventory = [ Sim.Food, 6; Sim.Spice, 4 ] }
+        | Scholar -> { Kind = Scholar; InitialMoney = 70; InitialEnergy = 100.0f; InitialInventory = [ Sim.Food, 10; Sim.Scroll, 2 ] }
+
+    /// Placeholder carried in save v3 until the task-system slice lands (design §3).
+    type State =
+        { Profile: Profile
+          TaskToken: int
+          StoryStage: int }
+
+    let stateOf (kind: Kind) : State =
+        { Profile = profileOf kind; TaskToken = 0; StoryStage = 0 }