[Web runtime] Add reconnect-on-close to the Browser SDK

[minggangw]

Implements RosClient's previously-reserved reconnect option (web/client.js, _WsLink).

• {reconnect: true} reopens the WS link with exponential backoff (500ms\u201330s, half-jitter) after a drop that follows a successful connect. The first connect attempt always rejects once rather than retrying forever, even when a connection error is followed by a close event.
• Active subscriptions are replayed on reopen, reusing the same subId, so existing Subscription handles keep working transparently.
• RosClient.on/off lifecycle events: 'disconnected' (any unexpected drop), 'reconnecting' ({attempt, delay}), 'reconnected'.
• In-flight and new requests made during a drop or an active reconnect reject with code: 'connection_lost', with wording that reflects whether reconnecting is actually happening.
• ros.close() always wins over reconnect and finalizes cleanly, including when called mid-backoff.
• web/index.d.ts: reconnect documented as implemented; new RosClientEventMap/ReconnectingDetail; on/off declared on RosClient.
• test/test-web-reconnect.js (new, 8 tests): reconnect + subscription replay, in-flight/new-request rejection during a drop, default behavior with reconnect unset, first-connect-rejects-once, close() during backoff, close() never triggers a reconnect.

Fix: #1510

[Copilot]

Pull request overview

This PR enhances the rclnodejs/web Browser SDK’s resilience by adding WebSocket reconnect-on-close with backoff and HTTP retry-with-backoff behavior, plus corresponding public typings and tests.

Changes:

• Implement WebSocket reconnect-on-close with exponential backoff + jitter, subscription replay, and lifecycle events (disconnected/reconnecting/reconnected).
• Add HTTP retry-with-backoff for call()/publish() on network errors and 5xx responses via httpRetries.
• Add a new test suite covering WS reconnect behavior and HTTP retries.

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 4 comments.

File	Description
web/index.d.ts	Updates public types/docs to expose reconnect, httpRetries, and lifecycle event on/off APIs.
web/client.js	Implements reconnect/backoff logic (WS + HTTP), lifecycle event listeners, and wires new options into transports.
test/test-web-reconnect.js	Adds coverage for WS reconnect semantics and HTTP retry behavior.

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[coveralls]

coverage: 91.068% (-0.001%) from 91.069% — minggangw:feat/web-sdk-reconnect into RobotWebTools:develop

[Copilot]

Pull request overview

Copilot reviewed 2 out of 3 changed files in this pull request and generated no new comments.

Suppressed comments (3)

web/client.js:147

• When close() aborts a reconnect attempt before its socket opens, opened is false, so this handler only rejects the open promise and never reaches _handleClose()/_finalizeClosed(). The retry stops because _userClosed is set, but _closed remains false and _reconnecting remains true, causing later operations to report connection_lost indefinitely after close() has resolved. Finalize the link when this pre-open close was user initiated.

      const onClose = () => {
        if (opened) {
          this._handleClose();
          return;
        }
        if (!settled) {
          settled = true;
          reject(new Error('connection closed before it was established'));
        }

web/client.js:505

• The PR promises configurable HTTP retries via httpRetries, but the newly added option plumbing only forwards reconnect; _HttpLink is still constructed without options and performs exactly one fetch() for network errors and 5xx responses. ConnectOptions also exposes no httpRetries, and the added suite contains only WebSocket tests. Implement and type the advertised HTTP retry option (with its retry tests), or remove HTTP retry from this PR's stated scope.

    this._wsOptions = {
      reconnect: !!options.reconnect,
      onEvent: (name, detail) => this._emit(name, detail),
    };

web/client.js:180

• disconnected listeners run synchronously before the link enters either _reconnecting or _closed. If a listener immediately starts a request, both guards still pass and _sendRaw targets the already-closed socket, producing a transport-specific send error instead of the expected connection_lost/terminal-close result. Transition the state and fail in-flight work before emitting the event, while keeping disconnected before _scheduleReconnect() so lifecycle ordering remains intact.

    this._onEvent('disconnected', undefined);