support dashboard websocket attach on Node 20

[PAW122]

Fixes two dashboard-embedded TUI failures:

- prevents a React render-phase update loop by removing the eager ensureAgentsNudgeConfig() call from gateway event handler creation
- fixes gateway exited / gateway websocket unavailable in the dashboard when the PTY child runs under Node 20, where globalThis.WebSocket may be unavailable

The gateway client now resolves a runtime WebSocket constructor by using:

1. globalThis.WebSocket when available
2. require("undici").WebSocket as a fallback for Node 20

This keeps dashboard /chat attach mode working with the Node runtime used by the system service.

Root cause

The dashboard launches the embedded TUI through /usr/bin/node, which on this host is Node v20.19.2. In that runtime:

txt
typeof WebSocket === "undefined"


Manual CLI checks used a newer node from PATH where WebSocket exists globally, so the issue only reproduced inside the dashboard PTY path.

Because attach mode depends on HERMES_TUI_GATEWAY_URL, the TUI exited early with:

txt
gateway websocket unavailable
gateway exited


Changes

- Add resolveRuntimeWebSocket() in ui-tui/src/gatewayClient.ts
- Use the resolved WebSocket constructor for:
  - gateway attach mode
  - sidecar mirror connection
- Add HERMES_TUI_DISABLE_UNDICI_WEBSOCKET=1 test switch so tests can still simulate a runtime with no WebSocket support
- Update gateway client tests for the fallback behavior
- Remove eager nudge config fetch during gateway handler creation to avoid render-phase RPC/state updates

Test plan

Ran:

bash
npm test -- gatewayClient.test.ts


Result:

txt
10 tests passed


Ran:

bash
npm run build


Result:

txt
built ui-tui/dist/entry.js


Verified dashboard /chat locally with the same Node runtime used by the service:

txt
/usr/bin/node --expose-gc /home/pawiu/.hermes/hermes-agent/ui-tui/dist/entry.js


Dashboard verification:

- gateway exited: false
- gateway websocket unavailable: false
- React errors: 0
- resumed session renders correctly in /chat

[teknium1]

Thanks for the focused dashboard/TUI investigation. This is an automated hermes-sweeper review; the requested behavior is already present on current main.

• Merged PR fix(ui-tui): stabilize embedded dashboard chat gateway #44528 implemented the same two fixes in e2145a5c9cae337fad64ab6cf34fed730c00595b (fix(ui-tui): stabilize embedded dashboard chat gateway), shipped in v2026.6.19.
• ui-tui/src/gatewayClient.ts:24-25 resolves Undici's WebSocket when the global constructor is unavailable; both sidecar and attached-gateway construction use it at :275 and :429-442.
• ui-tui/src/app/createGatewayEventHandler.ts:314-318 starts the nudge-config read from gateway.ready, rather than during render-time handler construction.
• Current regression coverage includes the missing-global-WebSocket fallback at ui-tui/src/__tests__/gatewayClient.test.ts:399-410 and deferred config loading at ui-tui/src/__tests__/createGatewayEventHandler.test.ts:1105-1126.