fix(gateway): close adapter resources when connect() fails or raises (#12339)

Gateway startup leaks aiohttp.ClientSession (and other partial-init
resources) when an adapter's connect() returns False or raises. The
adapter is never added to self.adapters, so the shutdown path at
gateway/run.py:2426 never calls disconnect() on it — Python GC later
logs 'Unclosed client session' at process exit.

Seen on 2026-04-18 18:08:16 during a double --replace takeover cycle:
one of the partial-init sessions survived past shutdown and emitted
the warning right before status=75/TEMPFAIL.

Fix:
- New GatewayRunner._safe_adapter_disconnect() helper — calls
  adapter.disconnect() and swallows any exception. Used on error paths.
- Connect loop calls it in both failure branches: success=False and
  except Exception.
- Adapter disconnect() implementations are already expected to be
  idempotent and tolerate partial-init state (they all guard on
  self._http_session / self._bridge_process before touching them).

Tests: tests/gateway/test_safe_adapter_disconnect.py — 3 cases verify
the helper forwards to disconnect, swallows exceptions, and tolerates
platform=None.

gateway/run.py

@@ -752,6 +752,26 @@ class GatewayRunner:
             chat_id for chat_id, mode in self._voice_mode.items() if mode == "off"
         )
 
+    async def _safe_adapter_disconnect(self, adapter, platform) -> None:
+        """Call adapter.disconnect() defensively, swallowing any error.
+
+        Used when adapter.connect() failed or raised — the adapter may
+        have allocated partial resources (aiohttp.ClientSession, poll
+        tasks, child subprocesses) that would otherwise leak and surface
+        as "Unclosed client session" warnings at process exit.
+
+        Must tolerate partial-init state and never raise, since callers
+        use it inside error-handling blocks.
+        """
+        try:
+            await adapter.disconnect()
+        except Exception as e:
+            logger.debug(
+                "Defensive %s disconnect after failed connect raised: %s",
+                platform.value if platform is not None else "adapter",
+                e,
+            )
+
     # -----------------------------------------------------------------
 
     def _flush_memories_for_session(
@@ -1913,6 +1933,15 @@ class GatewayRunner:
                     logger.info("✓ %s connected", platform.value)
                 else:
                     logger.warning("✗ %s failed to connect", platform.value)
+                    # Defensive cleanup: a failed connect() may have
+                    # allocated resources (aiohttp.ClientSession, poll
+                    # tasks, bridge subprocesses) before giving up.
+                    # Without this call, those resources are orphaned
+                    # and Python logs "Unclosed client session" at
+                    # process exit. Adapter disconnect() implementations
+                    # are expected to be idempotent and tolerate
+                    # partial-init state.
+                    await self._safe_adapter_disconnect(adapter, platform)
                     if adapter.has_fatal_error:
                         self._update_platform_runtime_status(
                             platform.value,
@@ -1953,6 +1982,10 @@ class GatewayRunner:
                         }
             except Exception as e:
                 logger.error("✗ %s error: %s", platform.value, e)
+                # Same defensive cleanup path for exceptions — an adapter
+                # that raised mid-connect may still have a live
+                # aiohttp.ClientSession or child subprocess.
+                await self._safe_adapter_disconnect(adapter, platform)
                 self._update_platform_runtime_status(
                     platform.value,
                     platform_state="retrying",