chore: bootstrap project scaffolding

Add architecture doc (research-wiki/ARCHITECTURE.md), CLAUDE.md with
tiered SOP for Fable 5, adapted .claude skills/hooks/settings, package
skeleton (src/polygateway), pyproject with import-linter contracts,
Makefile, .env.example and smoke test.

pyproject.toml

@@ -0,0 +1,69 @@
+[build-system]
+requires = ["setuptools>=68.0"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "polygateway"
+version = "0.1.0"
+description = "PolyGateway：实验室统一的大语言模型（LLM/VLM/OCR）调度与中转库——多源、限流、重试、熔断、缓存、遥测"
+requires-python = ">=3.11"
+dependencies = [
+    "httpx>=0.27",
+    "pydantic>=2.8",
+    "pydantic-settings>=2.4",
+    "loguru>=0.7",
+]
+
+[project.optional-dependencies]
+redis = ["redis>=5.0"]
+postgres = ["asyncpg>=0.29"]
+structured = ["json-repair>=0.28"]
+sdk = ["openai>=1.30"]
+dev = [
+    "pytest>=8.0",
+    "pytest-cov>=5.0",
+    "pytest-asyncio>=0.23",
+    "ruff>=0.6",
+    "radon>=6.0",
+    "import-linter>=2.0",
+]
+
+[tool.setuptools.packages.find]
+where = ["src"]
+
+[tool.pytest.ini_options]
+pythonpath = ["src"]
+testpaths = ["tests"]
+asyncio_mode = "auto"
+markers = [
+    "requires_redis: 需要可达的 Redis（无则 skip）",
+    "requires_llm: 需要真实 LLM 网关（无则 skip，输出落 tests/outputs/）",
+    "slow: 慢速测试（CI 按需跑）",
+]
+
+[tool.ruff]
+target-version = "py311"
+line-length = 100
+
+[tool.ruff.lint]
+select = ["E", "F", "W", "I", "N", "UP", "B", "A", "C4", "SIM", "TCH"]
+ignore = ["E501"]
+
+[tool.ruff.lint.isort]
+known-first-party = ["polygateway"]
+
+# 依赖纪律（ARCHITECTURE.md §8）：ports/types/errors/streaming 为最内层；
+# middleware 只依赖端口；transports/backends/telemetry/structured/providers/sources
+# 只实现端口且互不依赖；client 是唯一组装层。
+# 注：M1 模块落地前 lint-imports 由 Makefile 门控跳过。
+[tool.importlinter]
+root_packages = ["polygateway"]
+
+[[tool.importlinter.contracts]]
+name = "洋葱分层：client → 实现层 → 内核（ports/types/errors/streaming）"
+type = "layers"
+layers = [
+    "polygateway.client",
+    "polygateway.middleware : polygateway.transports : polygateway.backends : polygateway.telemetry : polygateway.structured : polygateway.providers : polygateway.sources",
+    "polygateway.ports : polygateway.types : polygateway.errors : polygateway.streaming",
+]