Point the slot range message at rp2040_ble and explain the import split

esphome/components/bluetooth_connection/__init__.py

@@ -106,8 +106,11 @@ async def _rp2_register(backend: cg.MockObj, config: ConfigType) -> None:
 
 @dataclass(frozen=True)
 class _PlatformBackend:
-    """One platform's backend: codegen class, extra schema keys (lazy so the
-    platform stack is only imported when targeted), and stack registration."""
+    """One platform's backend: codegen class, extra schema keys, and stack
+    registration. The esp32 fragments import their stack lazily because those
+    imports register esp32-only automations as a side effect; rp2040_ble is
+    side-effect-free, so it is imported at module scope (the cap constant
+    needs it there anyway)."""
 
     backend_class: cg.MockObjClass
     schema_fragment: Callable[[], cv.Schema]

esphome/components/bluetooth_proxy/__init__.py

@@ -185,8 +185,8 @@ def _rp2_config_schema() -> cv.All:
                         min=1,
                         max=max_conn,
                         msg=f"rp2 supports at most {max_conn} connection slot(s); "
-                        "the BTstack pool overrides in bluetooth_connection "
-                        f"are sized for {max_conn}",
+                        "the BTstack pool overrides in rp2040_ble are sized "
+                        f"for {max_conn}",
                     ),
                 ),
             }