fix(connections): handle IMAP errors to prevent crash on idle timeout

[hazzcomm]

Summary

When the IMAP server closes an idle connection (e.g. Dovecot's default 5-minute socket timeout), imapflow emits an 'error' event on the client. Since no handler is attached, Node crashes with:

node:events:487
      throw er; // Unhandled 'error' event

Error: Socket timeout
    at TLSSocket.<anonymous> (.../imapflow/lib/imap-flow.js:875:29)
    code: 'ETIMEOUT'

This takes the MCP server down and requires a Claude Desktop restart to recover.

Fix

Attach an error handler to the ImapFlow client after connect(). On error, log it and remove the client from the map. The existing usable check in getImapClient() already handles reconnection on the next tool call — it just needs the process to stay alive to reach it.

client.on('error', (err: Error) => {
  mcpLog('warning', 'imap', `IMAP connection lost for "${accountName}": ${err.message}`).catch(() => {});
  this.imapClients.delete(accountName);
});

The change is 11 lines. All 150 unit tests pass.

Test plan

• pnpm check clean
• pnpm typecheck clean
• pnpm test — 150/150 pass
• Manual idle test: leave server idle >5 minutes, verify next tool call reconnects without crash

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