fix(@typedtrader/exchange): reconnect Alpaca WebSocket in-process instead of exiting

[bennycode]

Summary

• The Alpaca market-data WebSocket close handler called process.exit(1) so an external orchestrator could restart the stream. Library code must not kill the process — it takes down every other trading session, price watch, and the Telegram bot sharing the same process.
• On an unexpected close, AlpacaWebSocket now reconnects in-process using the existing ts-retry-promise config (30s delay, infinite retries, non-retryable close codes 402/404/405/409), re-authenticates, and re-subscribes all previously subscribed bar topics under the same connectionId — consumers holding an AlpacaConnection keep working transparently.
• The manager now extends EventEmitter and emits reconnecting, resubscribed, and reconnect_failed (each with the connectionId) so hosts can log/alert on stream drops.
• New disconnect(connectionId) closes a connection intentionally; a guard flag ensures an intentional close never triggers reconnection (mirrors the AlpacaTradingWebSocket sibling API).
• Fixes a latent listener leak: subscribeToBars attached a new stream.on('message') handler on every call and unsubscribeFromBars never removed it, so repeated subscribe cycles emitted duplicate candles. Each connection now has exactly one message handler that dispatches to tracked per-symbol callbacks — which is also what makes resubscription after a reconnect possible.
• Checked the sibling AlpacaTradingWebSocket: it has no exit-on-close pattern, so no change needed there.

Test plan

• New AlpacaWebSocket.test.ts with a stubbed AlpacaStream (vi.mock) covering:
  • unexpected close → reconnect + resubscribe of prior bar topics (and bars keep flowing afterwards)
  • intentional disconnect() → no reconnect
  • subscribe/unsubscribe/subscribe cycle → exactly one candle emission per message
  • process.exit is never called (spy)
  • singleton connection reuse per apiKey:source and symbol-scoped dispatch
• npm test in packages/exchange: 9 files, 92 tests passed
• npm run lint in packages/exchange: 0 errors

[Copilot]

Pull request overview

This PR updates the Alpaca market-data WebSocket manager to avoid terminating the entire Node.js process on unexpected socket closes, and instead reconnects in-process while preserving the same connectionId and bar subscriptions for existing consumers.

Changes:

• Replace process.exit(1) on unexpected close with in-process reconnect + re-auth + resubscribe using existing ts-retry-promise policy.
• Rework bar subscription handling to avoid message-listener leaks by dispatching through a single per-connection message handler and tracked per-symbol callbacks.
• Add lifecycle events (reconnecting, resubscribed, reconnect_failed) and an explicit disconnect(connectionId) API, plus a new Vitest suite covering reconnect and subscription behavior.

Reviewed changes

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

File	Description
packages/exchange/src/broker/alpaca/AlpacaWebSocket.ts	Implements reconnect-in-process, event emission, intentional disconnect guard, and subscription dispatch refactor.
packages/exchange/src/broker/alpaca/AlpacaWebSocket.test.ts	Adds tests for reconnect/resubscribe behavior, intentional disconnect, listener leak regression, and “no process.exit” guarantee.

Comments suppressed due to low confidence (1)

packages/exchange/src/broker/alpaca/AlpacaWebSocket.ts:74

• If the stream emits an error during connection establishment, the promise rejects but the underlying WebSocket is left open. With retry() this can leave orphaned sockets between attempts and potentially contribute to connection-limit issues. Close the stream before rejecting so failed attempts are cleaned up.

      stream.on('error', (error: unknown) => {
        console.error(`WebSocket streaming failed for ID "${connectionId}".`, error);
        reject(error);
      });

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