feat(aiturk): hide what the paired IDE cannot serve, plain error sentences, reconnect on return

When paired with AITURK IDE:
- an "unknown method" (-32601) answer and the proxy's 403/route-404 are shown
  as plain sentences, never as raw JsonRpcError text; a method the IDE does
  not have is not sent again on the same socket
- Account connectors, Vault, Keys and Files are hidden (the IDE has no
  connectors.* / vault.* and its phone proxy refuses /api/env and /api/files)
- an idle-closed chat socket is reopened when the app returns to the
  foreground; idle tunnel connections are dropped on a network change
- an unsaved chat no longer polls /api/sessions/<id>
- the pairing screen shows the app version

A plain Hermes connection is unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01B8ppceaR5s6cvMnm7uGRnf

app/src/main/java/com/m57/hermescontrol/Navigation.kt

@@ -52,7 +52,9 @@ import com.m57.hermescontrol.data.local.AuthManager
 import com.m57.hermescontrol.data.ws.ConnectionStatus
 import com.m57.hermescontrol.data.ws.HermesWsClient
 import com.m57.hermescontrol.theme.LocalHermesStatusColors
+import com.m57.hermescontrol.ui.aiturkpair.AiturkFeatureGate
 import com.m57.hermescontrol.ui.aiturkpair.AiturkPairDeepLinkEffect
+import com.m57.hermescontrol.ui.aiturkpair.AiturkUnavailableScreen
 import com.m57.hermescontrol.ui.common.DisableDrawerGestures
 import com.m57.hermescontrol.ui.common.DrawerGestureController
 import com.m57.hermescontrol.ui.common.LocalDrawerGestureController
@@ -115,7 +117,11 @@ private fun appEntryProvider(
 
     ScreenRegistry.ALL_SCREENS.forEach { screen ->
         addEntryProvider(clazz = screen.key::class) {
-            screen.content(sessionId, openDrawer)
+            if (AiturkFeatureGate.shows(screen.key)) {
+                screen.content(sessionId, openDrawer)
+            } else {
+                AiturkUnavailableScreen(titleRes = screen.labelRes, onOpenDrawer = openDrawer)
+            }
         }
     }
 
@@ -325,6 +331,7 @@ fun MainNavigation(sessionId: String? = null) {
                         )
                         ScreenRegistry.ALL_SCREENS
                             .filter { it.drawerSection == section }
+                            .filter { AiturkFeatureGate.shows(it.key) }
                             .forEach { entry ->
                                 NavigationDrawerItem(
                                     icon = { Icon(entry.icon, contentDescription = null) },