feat(proxy): T-X6 模型池能力位过滤——vision/tools/context 硬过滤（采纳 cortiq capabilities）

- model_pool：条目新增 capabilities{vision,tools,context_window}，
  归一化缺省全兼容（老条目行为零变化；非法形态回落缺省）；
  filter_by_capabilities 硬过滤（context_window=0 视为不限）
- proxy routes：_request_needs 从请求体推断需求（多模态 image_url → vision、
  tools 非空 → tools、上下文需求 = 字符/3 + min(max_tokens,4096) 与预扣同口径）；
  条目不满足时在池内重定向到首个合格条目
- 与 T-X1/T-X2 组合语义：能力重定向 → 预算降档 → 降级链，逐级独立不互扰

pytest 461 passed（T-X3 后 455 + 6）

tests/test_model_pool_capabilities.py

@@ -0,0 +1,94 @@
+"""模型池能力位过滤测试（T-X6）：归一化缺省 / 硬过滤 / 请求需求推断。"""
+import pytest
+
+from gateway.model_pool import PoolStore, filter_by_capabilities
+from gateway.proxy.routes import _entry_meets, _request_needs
+
+pytest.importorskip("fastapi")
+
+
+def _make_pool(tmp_path) -> PoolStore:
+    store = PoolStore(path=tmp_path / "pool.json")
+    store.upsert({"id": "text-only", "name": "纯文本", "tier": "budget",
+                  "backend": "openai", "base_url": "http://a", "model": "text-m",
+                  "capabilities": {"vision": False, "tools": True,
+                                   "context_window": 8192},
+                  "enabled": True})
+    store.upsert({"id": "vision", "name": "多模态", "tier": "premium",
+                  "backend": "openai", "base_url": "http://b", "model": "vision-m",
+                  "capabilities": {"vision": True, "tools": True,
+                                   "context_window": 32768},
+                  "enabled": True})
+    store.upsert({"id": "legacy", "name": "老条目", "tier": "local",
+                  "backend": "llama_server", "base_url": "http://c",
+                  "model": "legacy-m", "enabled": True})   # 无 capabilities 字段
+    return store
+
+
+def test_capabilities_default_full_compat(tmp_path):
+    """未声明能力位的老条目：缺省全兼容（vision/tools True、context 0 不限）。"""
+    pool = _make_pool(tmp_path)
+    e = pool.find_by_model("legacy-m")
+    assert e["capabilities"] == {"vision": True, "tools": True, "context_window": 0}
+
+
+def test_capabilities_invalid_shapes_fall_back(tmp_path):
+    pool = _make_pool(tmp_path)
+    pool.upsert({"id": "weird", "name": "怪", "tier": "budget", "backend": "openai",
+                 "base_url": "http://d", "model": "weird-m",
+                 "capabilities": {"vision": "是", "context_window": "abc"},
+                 "enabled": True})
+    cap = pool.find_by_model("weird-m")["capabilities"]
+    assert cap["vision"] is True          # 非布尔按缺省
+    assert cap["context_window"] == 0     # 非整数回落不限
+
+
+def test_filter_by_capabilities_hard_rules():
+    entries = [{"capabilities": {"vision": False, "tools": True, "context_window": 8192}},
+               {"capabilities": {"vision": True, "tools": True, "context_window": 32768}},
+               {"capabilities": {"vision": True, "tools": False, "context_window": 0}}]
+    out = filter_by_capabilities(entries, need_vision=True)
+    assert len(out) == 2
+    out = filter_by_capabilities(entries, need_vision=True, need_tools=True)
+    assert len(out) == 1
+    out = filter_by_capabilities(entries, need_vision=True, need_tools=True,
+                                 min_context_tokens=16384)
+    assert len(out) == 1 and out[0]["capabilities"]["context_window"] == 32768
+    # context_window=0（不限）不受 min_context 约束
+    out = filter_by_capabilities(entries, min_context_tokens=999999)
+    assert len(out) == 1 and out[0]["capabilities"]["context_window"] == 0
+
+
+def test_request_needs_detection():
+    body = {"messages": [
+        {"role": "user", "content": "普通文本问题"},
+        {"role": "user", "content": [{"type": "text", "text": "看这张图"},
+                                     {"type": "image_url",
+                                      "image_url": {"url": "data:image/png;base64,x"}}]},
+    ], "tools": [{"type": "function", "function": {"name": "f"}}],
+        "max_tokens": 3000}
+    needs = _request_needs(body)
+    assert needs["vision"] is True and needs["tools"] is True
+    assert needs["min_context_tokens"] > 3000
+
+    plain = _request_needs({"messages": [{"role": "user", "content": "hi"}]})
+    assert plain["vision"] is False and plain["tools"] is False
+    assert plain["min_context_tokens"] > 0
+
+
+def test_entry_meets_defaults_and_limits():
+    legacy = {"capabilities": {"vision": True, "tools": True, "context_window": 0}}
+    assert _entry_meets(legacy, {"vision": True, "tools": True,
+                                 "min_context_tokens": 999999})
+    limited = {"capabilities": {"vision": True, "tools": True, "context_window": 4096}}
+    assert _entry_meets(limited, {"vision": False, "tools": False,
+                                  "min_context_tokens": 4096})
+    assert not _entry_meets(limited, {"vision": False, "tools": False,
+                                      "min_context_tokens": 4097})
+
+
+def test_pool_list_returns_capabilities(tmp_path):
+    """list() 打码输出保留 capabilities 字段（前端可见）。"""
+    pool = _make_pool(tmp_path)
+    e = next(x for x in pool.list()["entries"] if x["id"] == "vision")
+    assert e["capabilities"]["vision"] is True