/effort without arguments should show interactive slider UI

Description

In previous versions (or certain environments), running /effort without arguments displayed an interactive slider UI where users could select the effort level using arrow keys:

Effort

Faster                                    Smarter

low    medium    high    xhigh    max    ultracode

←/→ to adjust · Enter to confirm · Esc to cancel

Currently, /effort without arguments only displays the current effort level, requiring users to type the exact level (e.g., /effort max).

Why this matters

When context reaches its limit and a new session must be started, users need to reconfigure the effort level each time. Having the interactive slider UI makes this quick and discoverable, especially for users who don't remember all available levels (low, medium, high, xhigh, max, ultracode).

Expected behavior

/effort without arguments should show the interactive slider UI for selecting the effort level.

Environment

• Claude Code v2.1.170
• macOS (VS Code integrated terminal)