feat(model): 按 provider 形状独立适配推理开关 + per-persona 提供商链真接线（裁决 03.4.2/08.4.1/03.4.1 余项）

- 新增 reasoning_shape.go：**每个 provider 形状一个 resolver，只发自己形状的字段**
  · deepseek：thinking{type} + reasoning_effort（依据 DevDocs/reference/deepseek 官方本地副本）
  · vllm：chat_template_kwargs.enable_thinking　· dashscope：顶层 enable_thinking（**只允许显式声明**）
  · openai：仅 reasoning_effort　· anthropic：自己的 thinking{budget_tokens}（未改）
  · 未知 kind → WARN 且一个字段都不发（不许静默失效）
- 形状载体：models.json 组级 `reasoning.kind`（可热更新，未声明则不写该键）+ env `LLM_REASONING_KIND`
- 红线：`effort:none` 在只有布尔开关的形状上翻成**显式关思考**，绝不降成任何强度档
- 03.4.1 余项：`Request.PersonaID` + `RuntimeLLM.ForPersona(pid)` 视图；
  每 persona 协议一条链并消费 `RouteProviderForPersona`；`agent/request.go` 非流式路径同一钩子
- **生产装配（主会话补）**：默认 agent 与 personaAgentPool 都改用 `ForPersona(pid)` 视图——
  否则角色级模型/提供商路由在生产里永不被选中（形同虚设）
- 复核：build/vet 绿 + model/agent/config/cmd 包测试绿；5 条变异反证先红后还原
  （其中一条「红但没钉住」已改用例：通道读取加 2s 超时，避免整包 panic 掩盖信号）
- 未落：DashScope 的 auto 推断（缺官方依据，只允许显式声明）；Qwen `/think` 前导消息
  （design/01 §2.1 与 design/11 §3 口径冲突，停手报告）

internal/runtime/model/model.go

@@ -172,6 +172,21 @@ type Request struct {
 	MaxTokens int
 	// Purpose labels the call for CallRecord accounting (e.g. "chat").
 	Purpose string
+	// PersonaID is the persona this turn answers as — the persona-level routing
+	// key of 裁决 03.4.1, as opposed to the LLM message role. RuntimeLLM reads it
+	// to pick the persona's provider chain (models.json personaProviders, i.e. a
+	// cross-protocol per-persona route). Empty means "no persona binding": the
+	// active group's default chain serves the request, so every pre-existing
+	// caller behaves exactly as before.
+	//
+	// Why a request field and not a context key: the decision happens at the
+	// adapter boundary that already carries the Request, and the value is
+	// per-call metadata of the same kind as Model/Purpose. The persona lives in
+	// the loop's private session-env context key, which the model package cannot
+	// read (model must not import loop), so a ctx carrier would have needed the
+	// same write anyway — with the decision hidden behind an invisible key and
+	// hard to assert across packages.
+	PersonaID string
 	// Tools is the interface-level placeholder for M2 function calling.
 	Tools []ToolSpec
 	// ToolChoice optionally directs how the provider selects a tool. It is an