fix: import the ThinkingWire that __all__ already promised

The previous commit added the name to __all__ but never bound it, so
`from polygateway import ThinkingWire` and `import *` both raised while
the whole suite stayed green — the export test names symbols one by one,
and nobody thought to add the new one.

The guard is now the invariant rather than a longer list: every name in
__all__ must be an attribute of the package.

src/polygateway/__init__.py

@@ -22,7 +22,12 @@ from polygateway.errors import (
 )
 from polygateway.ocr import OcrClient
 from polygateway.pricing import ModelPrice, PricingTable
-from polygateway.providers import DEFAULT_PROFILES, ProviderProfile, register_provider
+from polygateway.providers import (
+    DEFAULT_PROFILES,
+    ProviderProfile,
+    ThinkingWire,
+    register_provider,
+)
 from polygateway.telemetry.schema import telemetry_schema_sql
 from polygateway.thinking import (
     ThinkingCapability,

tests/unit/test_package.py

@@ -66,6 +66,7 @@ def test_thinking_public_surface_exported():
         "ThinkingCapability",
         "ThinkingObservation",
         "ThinkingUnsupportedError",
+        "ThinkingWire",
         "get_capability",
         "register_capability",
         "resolve_thinking",
@@ -74,3 +75,14 @@ def test_thinking_public_surface_exported():
         assert name in polygateway.__all__, name
     assert "observe_thinking" not in polygateway.__all__
     assert "reconcile_thinking" not in polygateway.__all__
+
+
+def test_every_promised_export_is_actually_importable():
+    """`__all__` 里的每个名字都必须真的绑在包上。
+
+    只维护 `__all__` 而漏掉 import,`from polygateway import X` 与 `import *`
+    都会当场炸,而逐个点名的用例只覆盖它当时想到的符号——2026-09-04 的
+    `ThinkingWire` 正是这样漏进来的(在 `__all__` 里躺了一个提交却 import 不到)。
+    """
+    missing = [name for name in polygateway.__all__ if not hasattr(polygateway, name)]
+    assert not missing, f"__all__ 承诺了但没绑上的符号: {missing}"