feat(toolbox): T6 创作工具箱通用生成器框架 — 8 新生成器 + 声明驱动落地页 + P2 收尾

通用执行路径驱动全部生成器（"加生成器=加一份声明"）：
- @llm: ww_agents +7 输出 schema + 7 spec（book-title/blurb/name/golden-finger/
  glossary/opening/fine-outline，只声明 tier）+ build_outline_chapter_context
- @backend: ww_skills GeneratorTool 描述符 + TOOLBOX(11) + get_tool；3 通用端点
  GET /skills/toolbox · POST .../skills/{tool_key}/generate(预览不写库,仅记账) ·
  POST .../ingest(复用 continuity 409 + partition_writes 白名单)；纯 context 派发
- @frontend: 工具箱落地页 RSC + 声明驱动 GeneratorRunner + lib/toolbox 纯函数
  + LeftNav「工具箱」+ ⌘K nav-toolbox/action-gen-*；legacy 3 跳现页
- @qa: tests/test_t6_toolbox_e2e.py 5 用例真 pg + mock 网关零 token，无端点 bug
- P2 收尾: 限流→decisions.md 记延后(单用户原型)；noopener/Committable 早已修

守不变量 #2(只声明 tier)/#3(预览不写库,入库经验收 gate)/#9(缓存前缀)。无 DB 迁移。
门禁绿: 后端 ruff/format/mypy 195/alembic 无漂移/pytest 583；前端 lint/tsc/vitest 279/build。
spec 回写 PRODUCT_SPEC §7 + ARCHITECTURE §7.2 端点表。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/web/lib/nav/items.test.ts

@@ -10,10 +10,10 @@ import {
 const PID = "p1";
 
 describe("projectNavItems", () => {
-  it("builds the eight project entries scoped to the project id", () => {
+  it("builds the nine project entries scoped to the project id", () => {
     const items = projectNavItems(PID);
 
-    expect(items).toHaveLength(8);
+    expect(items).toHaveLength(9);
     expect(items.map((i) => i.key)).toEqual([
       "write",
       "outline",
@@ -21,6 +21,7 @@ describe("projectNavItems", () => {
       "review",
       "style",
       "codex",
+      "toolbox",
       "rules",
       "skills",
     ]);