[BUG] /config dialog immediately dismissed without showing interactive UI

Description

Running /config in Claude Code immediately shows "Config dialog dismissed" instead of displaying the interactive settings UI with tabs.

Environment

• Claude Code version: 2.1.76
• OS: macOS (Darwin 25.3.0 arm64)
• Terminals tested: iTerm.app 3.6.9 (xterm-256color) AND macOS Terminal.app — same behavior in both
• Shell: zsh

Steps to Reproduce

1. Open a new claude session
2. Type /config
3. Observe: immediately prints "Config dialog dismissed" without showing any interactive UI

What I've Ruled Out

• Plugin interference: Removed all enabledPlugins and extraKnownMarketplaces from settings.json — still reproduces
• All custom config: Temporarily removed both ~/.claude/settings.json and ~/.claude/settings.local.json — still reproduces
• Terminal compatibility: Reproduced in both iTerm.app and macOS native Terminal.app
• Plan mode: Reproduces in normal REPL mode, not just plan mode
• Config syntax: JSON validated as correct; no hooks.json or .inputrc present
• Environment variables: No CI, NO_COLOR, or other suspicious env vars set

Expected Behavior

/config should open an interactive TUI dialog with multiple tabs for browsing and modifying settings.

Workaround

Manually editing ~/.claude/settings.json and ~/.claude/settings.local.json as a workaround.