feat: M4 文风 + M5 生成/多provider/Skill + Kimi Code 订阅接入 + 本地联调修复

M4（文风）: style-auditor 双轨（提取指纹/漂移第四审）+ jobs 长任务框架(zombie reaper) + 回炉 refine + GET /style read-back。
M5（生成+扩展）: worldbuilder/character-gen（入库 continuity 409 gate + partition_writes 白名单 + schema→JSONB 形变）；
  网关多 provider 回退链/熔断/能力降级（Anthropic/Gemini 适配器）；Skill registry + 表权限沙箱 + 规则；
  前端 角色生成器/世界观/Codex/规则页/技能库/⌘K 命令面板。
K1（Kimi Code 订阅接入）: OAuth device-flow（kimi-code）+ 静态 Console key（kimi-code-key）两路径；
  coding 端点 KimiCLI 伪造头（实测 UA allow-list 门禁，缺则 403）+ JSON 模式结构化（thinking ⊥ tool_choice）。
本地联调修复: CORS 中间件；assemble 注入 premise+「写第N章」指令（修空 prompt 400）；
  GET /outline·/draft read-back + 大纲/工作台/审稿页重载；写页 client/server 常量边界 + notFound 健壮化；
  字数 toLocaleString locale 水合；审稿页终稿从已存草稿 seed（修 accept 422）。
门禁: backend ruff/mypy(157)/alembic 无漂移/pytest 451 · frontend lint/tsc/vitest/build。

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

packages/llm_gateway/tests/test_capability_degradation.py

@@ -0,0 +1,109 @@
+"""T5.4 能力协商 / 降级（ARCH §4.4）。
+
+结构化输出：原生不支持时降级（instructor JSON-提示路径仍由适配器自处理；网关
+层负责在链内**优先选支持结构化输出的 provider**，无则降级到首个可用、对上层透明）。
+降级时 `served_by.degraded=True` 标注，记账/日志可见，正确性不受影响。
+"""
+
+from __future__ import annotations
+
+import uuid
+
+from fakes_resilience import FakeLedger, ScriptedAdapter, chain, chain_resolver
+from pydantic import BaseModel
+from ww_llm_gateway.adapters.base import Capabilities
+from ww_llm_gateway.gateway import Gateway
+from ww_llm_gateway.types import Block, LlmRequest, Scope
+
+
+class Tiny(BaseModel):
+    x: str
+
+
+def _structured_req() -> LlmRequest:
+    return LlmRequest(
+        tier="analyst",
+        input="给我结构化",
+        output_schema=Tiny,
+        scope=Scope(user_id=uuid.UUID(int=1)),
+    )
+
+
+async def test_prefers_structured_capable_provider_in_chain() -> None:
+    # 主 provider 不支持结构化输出，回退 provider 支持 → 网关优先选支持者服务结构化请求。
+    no_struct = ScriptedAdapter(
+        "weakprov",
+        capabilities_=Capabilities(structured_output=False, prefix_cache=False),
+    )
+    struct = ScriptedAdapter(
+        "strongprov",
+        capabilities_=Capabilities(structured_output=True, prefix_cache=True),
+    )
+    ledger = FakeLedger()
+    gw = Gateway(
+        {"weakprov": no_struct, "strongprov": struct},
+        ledger,
+        chain_resolver=chain_resolver(chain(("weakprov", "w"), ("strongprov", "s"))),
+    )
+
+    resp = await gw.run(_structured_req())
+
+    assert resp.served_by.provider == "strongprov"
+    assert resp.parsed is not None
+    assert no_struct.complete_calls == 0
+
+
+async def test_degrades_when_no_structured_capable_provider() -> None:
+    # 链上无 provider 支持结构化输出 → 降级用首个可用（适配器自走 instructor JSON 提示）
+    # 并标 served_by.degraded=True，不硬失败。
+    weak = ScriptedAdapter(
+        "weakprov",
+        capabilities_=Capabilities(structured_output=False),
+    )
+    gw = Gateway(
+        {"weakprov": weak},
+        FakeLedger(),
+        chain_resolver=chain_resolver(chain(("weakprov", "w"))),
+    )
+
+    resp = await gw.run(_structured_req())
+
+    assert resp.served_by.provider == "weakprov"
+    assert resp.served_by.degraded is True
+    assert weak.complete_calls == 1
+
+
+async def test_no_degradation_flag_for_plain_text() -> None:
+    # 纯文本请求对任何 provider 都不算降级。
+    weak = ScriptedAdapter("weakprov", capabilities_=Capabilities(structured_output=False))
+    gw = Gateway(
+        {"weakprov": weak},
+        FakeLedger(),
+        chain_resolver=chain_resolver(chain(("weakprov", "w"))),
+    )
+    req = LlmRequest(tier="writer", input="正文", scope=Scope(user_id=uuid.UUID(int=1)))
+
+    resp = await gw.run(req)
+
+    assert resp.served_by.degraded is False
+
+
+async def test_cache_blocks_passed_through_regardless_of_capability() -> None:
+    # 前缀缓存不支持时只是跳过，不改正确性、不算降级。
+    weak = ScriptedAdapter("weakprov", capabilities_=Capabilities(prefix_cache=False))
+    gw = Gateway(
+        {"weakprov": weak},
+        FakeLedger(),
+        chain_resolver=chain_resolver(chain(("weakprov", "w"))),
+    )
+    req = LlmRequest(
+        tier="writer",
+        input="正文",
+        system=[Block(text="世界观硬规则", cache=True)],
+        scope=Scope(user_id=uuid.UUID(int=1)),
+    )
+
+    resp = await gw.run(req)
+
+    assert resp.text
+    assert resp.served_by.degraded is False