[Docs] Sync recent user-facing behavior

[roomote-community]

​Created by Roomote. View the task or mention @roomote for follow-up asks.

What changed

• document newly shipped Roomote MCP channel discovery, Slack access rules, and refresh-token replay recovery
• explain the Doctor workflow, prompt composer file context, and environment setup credential deferral
• clarify GitHub automated skip behavior and correct the self-hosted web heap default

Why this change was made

A review of user-facing changes merged into develop during the previous 24 hours found public documentation that was missing or stale relative to shipped behavior.

Impact

Users and self-hosted operators now have accurate guidance for the affected workflows and configuration. There is no product runtime change.

[roomote-community]

No code issues found. See task

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