fix(app): replace greedy host runtime subscriptions with targeted hooks

useHostRuntimeSession returned the full HostRuntimeSnapshot, causing
every consumer to rerender on any internal state change (probe cycles,
client generation bumps). Replace with targeted hooks that return
primitives/stable references so useSyncExternalStore skips rerenders
when the subscribed value hasn't actually changed.

New hooks: useHostRuntimeClient, useHostRuntimeConnectionStatus,
useHostRuntimeLastError, useHostRuntimeAgentDirectoryStatus,
useHostRuntimeIsDirectoryLoading. Existing useHostRuntimeIsConnected
already followed this pattern.

useHostRuntimeSnapshot kept only for settings-screen where probe
data is legitimately needed.

packages/app/src/components/agent-input-area.tsx

@@ -28,7 +28,7 @@ import { Tooltip, TooltipContent, TooltipTrigger } from '@/components/ui/tooltip
 import { Shortcut } from '@/components/ui/shortcut'
 import { Autocomplete } from '@/components/ui/autocomplete'
 import { useAgentAutocomplete } from '@/hooks/use-agent-autocomplete'
-import { useHostRuntimeSession } from '@/runtime/host-runtime'
+import { useHostRuntimeAgentDirectoryStatus, useHostRuntimeClient, useHostRuntimeIsConnected } from '@/runtime/host-runtime'
 import {
   deleteAttachments,
   persistAttachmentFromBlob,
@@ -100,14 +100,16 @@ export function AgentInputArea({
   const insets = useSafeAreaInsets()
   const isScreenFocused = useIsFocused()
 
-  const { client, isConnected, snapshot } = useHostRuntimeSession(serverId)
+  const client = useHostRuntimeClient(serverId)
+  const isConnected = useHostRuntimeIsConnected(serverId)
+  const agentDirectoryStatus = useHostRuntimeAgentDirectoryStatus(serverId)
   const toast = useToast()
   const voice = useVoiceOptional()
   const isDictationReady =
     isConnected &&
-    (snapshot?.agentDirectoryStatus === 'ready' ||
-      snapshot?.agentDirectoryStatus === 'revalidating' ||
-      snapshot?.agentDirectoryStatus === 'error_after_ready')
+    (agentDirectoryStatus === 'ready' ||
+      agentDirectoryStatus === 'revalidating' ||
+      agentDirectoryStatus === 'error_after_ready')
 
   const agent = useSessionStore((state) => state.sessions[serverId]?.agents?.get(agentId))
 

packages/app/src/components/project-picker-modal.tsx

@@ -15,7 +15,7 @@ import { usePathname } from "expo-router";
 import { useKeyboardShortcutsStore } from "@/stores/keyboard-shortcuts-store";
 import { shortenPath } from "@/utils/shorten-path";
 import { useSessionStore } from "@/stores/session-store";
-import { useHosts, useHostRuntimeSession } from "@/runtime/host-runtime";
+import { useHosts, useHostRuntimeClient, useHostRuntimeIsConnected } from "@/runtime/host-runtime";
 import { useOpenProject } from "@/hooks/use-open-project";
 import { parseServerIdFromPathname } from "@/utils/host-routes";
 import { buildWorkingDirectorySuggestions } from "@/utils/working-directory-suggestions";
@@ -34,7 +34,8 @@ export function ProjectPickerModal() {
     return daemons[0]?.serverId ?? null;
   }, [pathname, daemons]);
 
-  const { client, isConnected } = useHostRuntimeSession(serverId ?? "");
+  const client = useHostRuntimeClient(serverId ?? "");
+  const isConnected = useHostRuntimeIsConnected(serverId ?? "");
   const workspaces = useSessionStore((state) =>
     serverId ? state.sessions[serverId]?.workspaces : undefined
   );

packages/app/src/components/terminal-pane.tsx

@@ -19,7 +19,7 @@ import Svg, {
 import { StyleSheet, UnistylesRuntime, useUnistyles } from "react-native-unistyles";
 import type { ListTerminalsResponse } from "@server/shared/messages";
 import { encodeTerminalKeyInput } from "@server/shared/terminal-key-input";
-import { useHostRuntimeSession } from "@/runtime/host-runtime";
+import { useHostRuntimeClient, useHostRuntimeIsConnected } from "@/runtime/host-runtime";
 import { useKeyboardShiftStyle } from "@/hooks/use-keyboard-shift-style";
 import {
   hasPendingTerminalModifiers,
@@ -150,7 +150,8 @@ export function TerminalPane({
   });
 
   const queryClient = useQueryClient();
-  const { client, isConnected } = useHostRuntimeSession(serverId);
+  const client = useHostRuntimeClient(serverId);
+  const isConnected = useHostRuntimeIsConnected(serverId);
 
   const scopeKey = useMemo(() => terminalScopeKey({ serverId, cwd }), [serverId, cwd]);
   const terminalsQueryKey = useMemo(() => ["terminals", serverId, cwd] as const, [cwd, serverId]);