feat(gateway): make health monitor stale threshold and max restarts configurable (openclaw#42107)

Verified:
- pnpm exec vitest --run src/config/config-misc.test.ts -t "gateway.channelHealthCheckMinutes"
- pnpm exec vitest --run src/gateway/server-channels.test.ts -t "health monitor"
- pnpm exec vitest --run src/gateway/channel-health-monitor.test.ts src/gateway/server/readiness.test.ts
- pnpm exec vitest --run extensions/feishu/src/outbound.test.ts
- pnpm exec tsc --noEmit

Co-authored-by: rstar327 <114364448+rstar327@users.noreply.github.com>
Co-authored-by: Tak Hoffman <781889+Takhoffman@users.noreply.github.com>

src/config/types.googlechat.ts

@@ -4,6 +4,7 @@ import type {
   GroupPolicy,
   ReplyToMode,
 } from "./types.base.js";
+import type { ChannelHealthMonitorConfig } from "./types.channels.js";
 import type { DmConfig } from "./types.messages.js";
 import type { SecretRef } from "./types.secrets.js";
 
@@ -99,6 +100,8 @@ export type GoogleChatAccountConfig = {
   /** Per-action tool gating (default: true for all). */
   actions?: GoogleChatActionConfig;
   dm?: GoogleChatDmConfig;
+  /** Channel health monitor overrides for this channel/account. */
+  healthMonitor?: ChannelHealthMonitorConfig;
   /**
    * Typing indicator mode (default: "message").
    * - "none": No indicator