feat(v2): T09 预审与推进沙盘——运行只读视图、演示情景与界面守卫

覆盖 AC-11/12/29/30/31/42/44（BR-11/29/30/41/43、E-20/21/22）。

后端：
- contracts/simulation.py：Simulation/SimulationAssumption/ScenarioDimensionState。
  契约层直接禁止 production 域携带演示估计（E-21）；ready 必须有结果、
  failed 必须带错误码且不得显示结果、计算中不得预告乐观增幅。
- services/prescreen_sandbox.py：演示情景表（DEMO-TABLE-v1）与推演入口。
  组合查表不是单项加和（assert_not_additive 把这条写成可执行断言）；
  只改被假设的维度，其余维度原样保留；失败保留基线并标未完成。
- services/prescreen_store.py：运行视图只读存储，复用 assistant_objects 新 kind
  prescreen_run，不新建表；只提供保存与读取，要改结果必须产生新修订。
- api/prescreen.py：新增 3 个只读端点（运行列表、运行视图、可用假设动作）
  与 1 个情景端点；请求体里没有任何概率字段。越域返回 E-21、冲突假设 E-22、
  过期修订 409。
- contracts/prescreen.py：补 E-20/21/22 三个错误码与其 HTTP 映射。

前端（挂进既有工作台「材料与问题」页，不新建路由、不新增样式表）：
- src/lib/prescreen-run.ts：客户端契约、呈现判定（同刻度 3–8 维才画雷达）、
  演示值域判定、来源与数据域徽标（文字＋图标＋样式，去色仍可区分）。
- src/components/xingbang/PrescreenPanel.tsx：主审意见、演示值（紧邻固定说明）、
  维度雷达与等价文字列表、维度依据抽屉、假设勾选即时推演。
  旧请求晚到或结果与当前选择不一致即丢弃；请求失败保留基线并标未完成。
- scripts/test_prescreen_ui.cjs：界面源码守卫，已注册进 scripts/verify.py。

未做：运行装配结果的写入方仍是执行链路（T10 范围），当前由测试写入；
沙盘尚未接入真实执行，界面数值全部为服务端演示表值。

验证：backend 全量 unittest 469 项 OK；前端 npm run build 通过。

Co-Authored-By: Claude Code <noreply@anthropic.com>

backend/api/prescreen.py

@@ -41,7 +41,7 @@ from contracts.prescreen import (
     S1_ERROR_RETRYABLE,
 )
 from services import assistant_store as store
-from services import fact_conflict, material_import
+from services import fact_conflict, material_import, prescreen_sandbox, prescreen_store
 from services.assistant_settings import flags
 from services.fact_conflict import FactConflictUnresolved
 from services.project_assistant import ProjectAssistantService
@@ -84,6 +84,13 @@ class ResolveInput(Input):
     expected_revision: int = Field(ge=1)
 
 
+class SimulationInput(Input):
+    """T09 沙盘请求：只传假设动作键，不传任何概率或维度值。"""
+
+    assumptions: list[str] = Field(default_factory=list, max_length=8)
+    expected_revision: int | None = Field(default=None, ge=1)
+
+
 # ---------------------------------------------------------------- 错误信封
 def _envelope(request: Request, code: ErrorCode, message: str) -> JSONResponse:
     request_id = request.headers.get("x-request-id") or store.uid("req")
@@ -368,3 +375,80 @@ def resolve_fact_conflict(conflict_id: str, payload: ResolveInput, request: Requ
         return resolved
 
     return run(request, action)
+
+
+# ---------------------------------------------------------------- 运行视图（T09）
+@router.get("/projects/{project_id}/runs")
+def list_runs(project_id: str, request: Request, limit: int = 20):
+    """项目内已装配的预审运行视图列表；没有运行就返回空列表，不造空壳。"""
+    blocked = scope(request, project_id)
+    if blocked is not None:
+        return blocked
+
+    def action():
+        with _db() as db:
+            items = prescreen_store.listing(db, project_id, _limit(limit))
+        return {"items": items}
+
+    return run(request, action)
+
+
+@router.get("/projects/{project_id}/runs/{run_id}")
+def get_run(project_id: str, run_id: str, request: Request):
+    """只读运行视图。没有运行就是 404，不返回一个空壳运行充数。"""
+    blocked = scope(request, project_id)
+    if blocked is not None:
+        return blocked
+
+    def action():
+        with _db() as db:
+            return prescreen_store.load(db, project_id, run_id)
+
+    return run(request, action)
+
+
+@router.get("/projects/{project_id}/runs/{run_id}/assumptions")
+def list_assumptions(project_id: str, run_id: str, request: Request):
+    """本次方案可用的假设动作。只返回指向该运行真实存在维度的动作（E-22）。"""
+    blocked = scope(request, project_id)
+    if blocked is not None:
+        return blocked
+
+    def action():
+        with _db() as db:
+            view = prescreen_store.load(db, project_id, run_id)
+        return {"items": prescreen_sandbox.available_assumptions(view),
+                "scenario_table_version": prescreen_sandbox.DEMO_TABLE_VERSION,
+                "label": prescreen_sandbox.DEMO_LABEL}
+
+    return run(request, action)
+
+
+@router.post("/projects/{project_id}/runs/{run_id}/simulations", status_code=201)
+def create_simulation(project_id: str, run_id: str, payload: SimulationInput,
+                      request: Request):
+    """按完整假设组合产出一条情景；真实运行只被读取（BR-11 / AC-11）。
+
+    演示值只在 demo 域返回（E-21）；假设冲突或指向不存在的维度按 E-22 拒绝。
+    请求体里没有任何概率字段——数值一律由服务端查表给出。
+    """
+    blocked = scope(request, project_id)
+    if blocked is not None:
+        return blocked
+
+    def action():
+        with _db() as db:
+            view = prescreen_store.load(db, project_id, run_id)
+        if payload.expected_revision is not None \
+                and view.get("revision") != payload.expected_revision:
+            raise store.Conflict("运行已有新版本，请刷新后重试")
+        try:
+            result = prescreen_sandbox.simulate(view, payload.assumptions)
+        except prescreen_sandbox.DemoEstimateForbidden as exc:
+            return _envelope(request, ErrorCode.DEMO_ESTIMATE_FORBIDDEN, str(exc))
+        except prescreen_sandbox.AssumptionConflict as exc:
+            return _envelope(request, ErrorCode.SCENARIO_ASSUMPTION_CONFLICT, str(exc))
+        prescreen_sandbox.assert_baseline_untouched(view, result)
+        return result
+
+    return run(request, action)