refactor(chat): split ChatPage into domain hooks under pages/chat

ChatPage.tsx (5937 lines) is now a 1772-line cross-domain wiring layer;
all logic moved verbatim into per-domain modules:

- queue/useChatTurnQueue: local queue, WebUI remote queue protocol,
  snapshot publishing
- runtime/useSendChatTurn: the full send pipeline (overrides, large-paste
  import, gateway bridge, title job, abort/error commit, agent/text turns)
- gateway/useGatewayRuntimeSnapshots + useGatewayBridgeReadiness +
  useGatewayStatus: run mirroring, edit_resend rebase/hydration readiness,
  connection status
- history/useSharedHistory + useBranchConversation
- workspace/useWorkspaceProjects (+Removal, +ProjectTerminals, +Overlays)
- runtime/useChatModelSelection, composer/useComposerDraftCache,
  hooks/useNotifyToasts, hooks/useTauriFileDrop
- pure modules: composerDraftText, providerRuntimeConfig,
  gatewayRuntimeStatusModel, workspaceProjectsModel, chatPageUtils;
  tauriTunnelClient moved to lib/tunnels
- JSX extractions: WorkspaceOverlayHost (lazy Monaco defs move along),
  ChatFileDropOverlay

Behavior-preserving: tsc clean, 1113 frontend tests green, mirror check
passes; verified by mechanical body-hash diff against the old file plus
multi-lens adversarial review (instance identity, escaping closures,
effect ordering, JSX prop parity).

Also un-ignores pages/chat/workspace/ from the bare `workspace` gitignore
rule so the new directory is actually tracked.

Author: su-fen

.gitignore

@@ -15,6 +15,8 @@ lerna-debug.log*
 workspace
 !crates/agent-gui/src-tauri/src/commands/workspace/
 !crates/agent-gui/src-tauri/src/commands/workspace/**
+!crates/agent-gui/src/pages/chat/workspace/
+!crates/agent-gui/src/pages/chat/workspace/**
 cert/
 node_modules
 dist

crates/agent-gui/src/lib/tunnels/tauriTunnelClient.ts

@@ -0,0 +1,55 @@
+import { invoke } from "@tauri-apps/api/core";
+import { listen } from "@tauri-apps/api/event";
+import type {
+  LocalTunnelClient,
+  TunnelCreateInput,
+  TunnelStateSnapshot,
+  TunnelUpdateInput,
+} from "./constants";
+
+export function createTauriTunnelClient(): LocalTunnelClient {
+  const listeners = new Set<(snapshot: TunnelStateSnapshot) => void>();
+  let unlistenPromise: Promise<() => void> | null = null;
+  const normalizeSnapshot = (payload: unknown): TunnelStateSnapshot => {
+    const raw = (payload ?? {}) as Partial<TunnelStateSnapshot>;
+    return {
+      revision: raw.revision ?? 0,
+      agentOnline: raw.agentOnline === true,
+      relay: raw.relay ?? null,
+      tunnels: raw.tunnels ?? [],
+      gatewayUnsupported: raw.gatewayUnsupported === true,
+    };
+  };
+  return {
+    subscribeTunnelState: (listener) => {
+      listeners.add(listener);
+      if (!unlistenPromise) {
+        unlistenPromise = listen<TunnelStateSnapshot>("gateway:tunnel-state", (event) => {
+          const snapshot = normalizeSnapshot(event.payload);
+          for (const subscriber of [...listeners]) {
+            subscriber(snapshot);
+          }
+        });
+      }
+      void invoke<TunnelStateSnapshot>("gateway_tunnel_state")
+        .then((payload) => {
+          if (listeners.has(listener)) {
+            listener(normalizeSnapshot(payload));
+          }
+        })
+        .catch(() => {});
+      return () => {
+        listeners.delete(listener);
+        if (listeners.size === 0 && unlistenPromise) {
+          const pending = unlistenPromise;
+          unlistenPromise = null;
+          void pending.then((unlisten) => unlisten()).catch(() => {});
+        }
+      };
+    },
+    createTunnel: (input: TunnelCreateInput) => invoke<void>("gateway_tunnel_create", { input }),
+    updateTunnel: (input: TunnelUpdateInput) => invoke<void>("gateway_tunnel_update", { input }),
+    closeTunnel: (id: string) => invoke<void>("gateway_tunnel_close", { tunnel_id: id }),
+    checkTunnel: (id?: string) => invoke<void>("gateway_tunnel_check", { tunnel_id: id }),
+  };
+}