Memory leak: TUI and Slack bot event listeners not cleaned up

[sauerdaniel]

Problem

Several event listeners in the TUI and Slack bot are never cleaned up:

TUI Sync Context (sync.tsx)

The sdk.event.listen() call returns an unsubscribe function that is never called:

// Listener never cleaned up
sdk.event.listen((e) => { ... })

Tooltip Component (tooltip.tsx)

Mouse event listeners (mouseenter, mouseleave) are added to elements but never removed on component unmount, causing accumulation.

Slack Bot (slack/index.ts)

• Sessions Map grows unbounded (no cleanup of old sessions)
• No graceful shutdown handling (SIGINT/SIGTERM)
• No limit on maximum concurrent sessions

Impact

• Event listeners accumulate over component lifecycles
• Sessions accumulate in Slack bot
• Memory grows continuously in long-running processes

Relates to #5363

Expected Behavior

• TUI event listeners should be unsubscribed in onCleanup
• Tooltip should remove event listeners on unmount
• Slack bot should clean up old sessions and handle shutdown