Document steering and the follow-up queue

[biswaroop1547]

Summary

• Add a "While Fluso is working" section to the Chat page: steering the run in progress, queuing follow-ups behind it, editing/promoting/canceling queued messages, and the paused queue after a stop or failure.
• Four dark-mode screenshots captured from the live UI: steer button with tooltip, active-run menu, queued tray, paused tray.
• Link from Quickstart and Going deeper.
• Add Cowork to the spell-check dictionary: main is red on cspell over features/imports.mdx.

Validation

• mint broken-links
• cspell clean repo-wide
• Rendered locally with mint dev and reviewed the page visually.

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