test(gateway): cover no eager platform install on startup sweep

Pin the contract that ``_apply_env_overrides`` consults ``is_connected``
before the install-triggering ``check_fn``: an unconfigured platform is
skipped without calling ``check_fn`` (no lazy install), while a configured
platform still has ``check_fn`` run and is auto-enabled. The first assertion
fails on the pre-fix unconditional sweep.

tests/gateway/test_startup_no_eager_platform_install.py

@@ -0,0 +1,100 @@
+"""Regression tests: ``_apply_env_overrides`` must not lazy-install platform
+SDKs for platforms the user has not configured.
+
+For adapter plugins, ``PlatformEntry.check_fn`` doubles as the lazy-installer
+(it pip-installs the platform SDK as a side effect — see e.g.
+``plugins/platforms/discord/adapter.py::check_discord_requirements``).  The
+enablement sweep in ``_apply_env_overrides`` used to call ``check_fn`` for
+*every* registered plugin platform unconditionally, so a single
+``load_gateway_config()`` — which the desktop/dashboard readiness probe
+(``GET /api/status``) awaits synchronously — pip-installed Discord, Telegram,
+Slack, Feishu and Dingtalk even with ``platforms: none``.  That blocked
+startup until every install finished and made the desktop app time out and
+boot-loop (stuck at 94%).
+
+The fix consults the cheap ``is_connected`` credential check FIRST and only
+runs the install-triggering ``check_fn`` for platforms that are already
+enabled or actually configured.  These tests pin that contract.
+"""
+
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from gateway.config import GatewayConfig, Platform, PlatformConfig, _apply_env_overrides
+from gateway.platform_registry import PlatformEntry, platform_registry
+
+
+@pytest.fixture
+def isolated_registry():
+    """Run with a registry containing only the entries the test registers."""
+    original = dict(platform_registry._entries)
+    platform_registry._entries.clear()
+    try:
+        # ``_apply_env_overrides`` calls ``discover_plugins()`` (idempotent),
+        # which would re-register the real bundled platforms and clobber the
+        # fakes below.  Neutralize it so the test controls the registry.
+        with patch("hermes_cli.plugins.discover_plugins", lambda *a, **k: None):
+            yield platform_registry
+    finally:
+        platform_registry._entries.clear()
+        platform_registry._entries.update(original)
+
+
+def _register_fake_platform(name, *, check_fn, is_connected):
+    platform_registry.register(
+        PlatformEntry(
+            name=name,
+            label=name.title(),
+            adapter_factory=lambda cfg: MagicMock(),
+            check_fn=check_fn,
+            is_connected=is_connected,
+            source="plugin",
+        )
+    )
+
+
+def test_unconfigured_platform_is_not_probed_for_install(isolated_registry):
+    # is_connected reports "no credentials" → the platform must be skipped
+    # without ever calling check_fn (which would lazy-install the SDK).
+    check_fn = MagicMock(return_value=True)
+    _register_fake_platform(
+        "discord", check_fn=check_fn, is_connected=lambda cfg: False
+    )
+
+    config = GatewayConfig()
+    _apply_env_overrides(config)
+
+    check_fn.assert_not_called()
+    assert not config.platforms.get(Platform.DISCORD, PlatformConfig()).enabled
+
+
+def test_configured_platform_is_still_installed_and_enabled(isolated_registry):
+    # is_connected reports "credentials present" → check_fn must run (so the
+    # SDK is verified/installed) and the platform is auto-enabled, exactly as
+    # before the fix.
+    check_fn = MagicMock(return_value=True)
+    _register_fake_platform(
+        "discord", check_fn=check_fn, is_connected=lambda cfg: True
+    )
+
+    config = GatewayConfig()
+    _apply_env_overrides(config)
+
+    check_fn.assert_called_once()
+    assert config.platforms[Platform.DISCORD].enabled is True
+
+
+def test_failed_install_does_not_enable_configured_platform(isolated_registry):
+    # Credentials present but the SDK genuinely cannot be installed/imported
+    # (check_fn returns False) → platform must not be enabled.
+    check_fn = MagicMock(return_value=False)
+    _register_fake_platform(
+        "discord", check_fn=check_fn, is_connected=lambda cfg: True
+    )
+
+    config = GatewayConfig()
+    _apply_env_overrides(config)
+
+    check_fn.assert_called_once()
+    assert not config.platforms.get(Platform.DISCORD, PlatformConfig()).enabled