[Bug] /config Output style picker lists only built-in styles; custom styles from user/project output-styles dirs are not listed (v2.1.231), while outputStyle setting loads them correctly

Environment: Claude Code v2.1.231 (CLI, macOS Darwin 24.6.0)

Summary: The /config → Output style picker lists only the four built-in styles (Default / Explanatory / Learning / Proactive). Custom output styles are never listed — from any documented discovery level — while the outputStyle settings key loads the same styles correctly, so listing and loading have diverged.

Repro:

1. Create a valid custom style, e.g. .claude/output-styles/my-style.md (project level) with frontmatter:

``markdown
---
name: My Style
description: test style
keep-coding-instructions: true
---
Test instructions.
``

1. Start a fresh session with the working directory inside the project. Run /config → Output style.
2. Observed: only the four built-ins are listed. My Style is absent.
3. Also tried: user level ~/.claude/output-styles/my-style.md (and a custom CLAUDE_CONFIG_DIR's output-styles/); fresh sessions; single-line-only frontmatter. Same result — never listed.

Loading works (the divergence): setting {"outputStyle": "My Style"} in .claude/settings.local.json DOES apply the style — a fresh session's replies follow the custom instructions, and the model self-reports the # Output Style: My Style block present in its system prompt, with keep-coding-instructions: true honored (built-in SE instructions retained).

Expected (per https://code.claude.com/docs/en/output-styles): custom styles saved at the user or project level appear in the /config Output style menu.

Impact: low once known (the settings key works), but confusing — users following the docs' create-then-pick flow conclude their style file is broken, since the picker gives no sign it exists. Possibly related surface: the /output-style command removal in v2.1.91 (picker is now the only interactive selection path).