[Feat] Add explicit steering to task messages

[roomote-roomote]

​Opened on behalf of @daniel-lxs. Follow up by mentioning @roomote-roomote, in the web UI, or in Slack.

What changed

• Added an optional steer flag to manage_tasks when using send_message.
• Kept ordinary follow-up messages on the task queue by default.
• Routed steer: true messages through immediate task steering while preserving the dedicated queued path for linked review handoffs.
• Documented the new contract in the MCP tool schema and covered both routing modes with tests.

Why this change was made

Callers need an explicit way to choose between a normal queued follow-up and an instruction that should interrupt the active turn immediately.

Impact

MCP clients can now steer an active task with send_message by passing steer: true. Existing calls without the flag remain non-interrupting and follow the task queue.

[roomote-community]

No code issues found. See task

_{Reviewed 00dc0cd}