Skill prefix namespace setting not applied + slash command descriptions too long

## Environment

- gstack version: v0.12.11.0
- Platform: Linux (WSL2)
- `skill_prefix` config: `true`

## Issue 1: Namespace prefix not applied

`gstack-config get skill_prefix` returns `true`, but slash commands still appear without the `gstack-` prefix. Running `./setup --prefix` does not change the behavior. The namespace setting seems to have no effect.

**Expected:** Commands should appear as `/gstack-qa`, `/gstack-ship`, `/gstack-review`, etc.
**Actual:** Commands still appear as `/qa`, `/ship`, `/review`, etc.

## Issue 2: Slash command descriptions are too long and wrap

Slash command descriptions in the command palette are excessively long, causing line wrapping. The wrapped text pushes below the command name, making it hard to scan and identify commands at a glance.

**Expected:** Short, single-line descriptions that stay on the same line as the command name.
**Actual:** Multi-line wrapped descriptions that break readability of the command list.