[codex] Handle webchat reconnect catch-up

[rockwellll]

Summary

• Reconnect the shared ActionCable socket after close or error, with debounced retry and active channel resubscription.
• Wait for WebchatChannel subscription confirmation before running webchat catch-up.
• Add a webchat messages catch-up request using after_id and insert recovered messages by timestamp so missed messages land before newer realtime messages.
• Rebuild lib and dist outputs.

Server dependency

• Requires backend catch-up endpoint from https://github.com/hellotext/hellotext/pull/4757

Why

When a deploy replaces the Docker image, the WebSocket can drop while the page is still open. The SDK now restores the subscription and asks the server for messages created after the last rendered persisted message, closing the small window where a message could otherwise be missed.

Validation

• yarn test
• yarn build
• git diff --check

---

Note

Medium Risk
Changes live messaging, reconnect, and message ordering; behavior depends on the new backend catch-up API and must stay aligned with realtime delivery.

Overview
Adds webchat reconnect recovery so an open widget can survive ActionCable drops (for example during deploys) without missing messages.

The shared ApplicationChannel now replaces dead sockets, debounces reconnects, replays message handlers, and resubscribes active channels after open. It also exposes onDisconnect and onSubscriptionConfirmed hooks for control frames.

WebchatChannel tracks subscription intent, resubscribe only when still subscribed, and runs onReconnect callbacks only after a matching confirm_subscription for this webchat/session/conversation.

WebchatMessagesAPI.catchUp fetches messages with after_id and session. WebchatController snapshots the last rendered message id on disconnect, calls catch-up after reconnect confirmation, and inserts recovered messages by created_at so backfill sits before newer realtime bubbles. lib/dist outputs are rebuilt.

Depends on the server catch-up endpoint in hellotext PR 4757.

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