feat(web): AI 立项方案生成+预填（种子门控 + 按字段接受）

向导阶段（project 未建）一键推演结构化书级蓝图预填立项向导。

- 新 SPEC project_plan_spec（analyst 档，纯预览 reads/writes=()）+ schema
  ProjectPlanResult（书名候选 + 时空背景/叙事结构/故事核心/结局设计/基调，
  全字段默认值守解析韧性）+ 注册 SCHEMA_CATALOG；计数三处 21→22 + regen golden。
- 端点 POST /skills/project-plan/generate（不带 project 前缀，绕开 toolbox 404）：
  请求体序列化向导草稿为 project_context，复用 build_brief_context + run_generator；
  种子门控（缺 genre/logline→422）；请求 schema 加 max_length 上界。
- run_generator/_build_request 的 project_id 放宽 uuid.UUID|None（向导无 project）。
- 前端 wizard.ts 加 mapPlanResultToWizardForm（错配字段折进 premise 不静默丢）+
  applyPlanPatch（仅回填空字段、保护已编辑）+ useProjectPlan hook + PlanAssistant。

packages/agents/ww_agents/__init__.py

@@ -38,6 +38,7 @@ from .schemas import (
     PaceIssue,
     PaceReview,
     PolishResult,
+    ProjectPlanResult,
     Scene,
     StyleDimension,
     StyleDriftReview,
@@ -68,6 +69,7 @@ from .specs import (
     opening_spec,
     outliner_spec,
     pace_spec,
+    project_plan_spec,
     refiner_spec,
     style_drift_spec,
     style_extract_spec,
@@ -111,6 +113,7 @@ __all__ = [
     "PaceIssue",
     "PaceReview",
     "PolishResult",
+    "ProjectPlanResult",
     "Scene",
     "StyleDimension",
     "StyleDriftReview",
@@ -139,6 +142,7 @@ __all__ = [
     "outliner_spec",
     "output_schema_for",
     "pace_spec",
+    "project_plan_spec",
     "refiner_spec",
     "style_drift_spec",
     "style_extract_spec",