Configurable Max Questions in Plan Mode

What variant of Codex are you using?

CLI

What feature would you like to see?

## Summary
Plan mode currently has a hard cap of 3 clarification questions. The question quality is strong, but complex tasks often need more than 3 to avoid assumptions.

## Problem
A fixed limit of 3 can reduce plan quality for multi-step or ambiguous work. It forces early assumptions when deeper clarification would be better.

## Proposal
Make the max number of Plan mode questions configurable.

• Keep default at 3 (no behavior change for existing users).
• Add configurable limit at workspace/session level, e.g. plan_mode.max_questions.
• Suggested range: 1–10.
• When limit is reached, Codex proceeds with explicit assumptions.

## Suggested UX/API

• Config example: plan_mode.max_questions: 6
• Optional per-run override: --plan-max-questions=6
• UI hint: “Question 2 of 6”

## Acceptance Criteria

1. Default remains 3 when unset.
2. If set to N, Codex can ask up to N questions in Plan mode.
3. Invalid values fail gracefully and fall back to default.
4. Logs/telemetry include configured question cap.