docs: document the AskUserQuestion plan-mode tool

[inference-gateway-maintainer]

Summary

Documents the new AskUserQuestion plan-mode tool in cli.md. In Plan Mode the agent can pause and ask the user 1-4 multiple-choice clarifying questions, then fold the answers back into the plan it submits via RequestPlanApproval.

Changes:

• Added AskUserQuestion to the Workflow row of the Tool Categories table.
• Added a dedicated #### AskUserQuestion subsection under Workflow Tools covering:
  • Purpose and when the agent uses it (clarify ambiguity before requesting plan approval).
  • The question/option schema - questions[] (1-4), each with header (chip, <= 12 chars), question, 2-4 options of {label, description}, and optional multiSelect; the auto-appended "Other" choice and the (Recommended) preselect suffix; plus a JSON example.
  • The keyboard controls (up/down navigate, space toggles multi-select, enter advances/submits, esc/ctrl+c cancels).
  • Plan-mode-only availability (read-only, no approval gate).
  • Headless graceful-degrade behavior (returns a "proceed with assumptions" result instead of blocking when no interactive user is reachable).
• Cross-referenced the tool from the Plan Mode section.

Source: inference-gateway/cli#652 (PR inference-gateway/cli#661).

Verified locally: bun run format:check, bun run lint:md, and bun run build all pass.

Closes #285

[inference-gateway-releaser]

🎉 This PR is included in version 0.6.114 🎉

The release is available on GitHub release

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