Slash command completion menu should appear for exact match (e.g. /editor)

Description

When typing a slash command that exactly matches a registered command name (e.g. /editor), the completion menu does not appear. Pressing the ↓ arrow key has no effect.

However, when typing a partial match (e.g. /edit), the completion menu correctly appears with /editor as a candidate, and pressing ↓ selects and fills it into the input.

Steps to Reproduce

1. Start kimi: uv run kimi
2. Type /editor (exact match) → no completion menu appears
3. Press ↓ → nothing happens
4. Clear input, type /edit (partial match) → completion menu appears showing /editor
5. Press ↓ → input is filled with /editor, menu item shows › selection indicator

Expected Behavior

The completion menu should also appear when the input exactly matches a command name. The user may want to:

• Confirm the command exists by seeing it in the menu
• Read the description before pressing Enter
• Navigate to other similar commands

Actual Behavior

Exact match suppresses the completion menu entirely. Only partial/fuzzy matches trigger it.

Environment

• kimi-cli version: 1.30.0
• OS: macOS

Start by reproducing the issue with uv run kimi, comparing /editor with /edit and the ↓ key behavior. Trace the slash-command completion handling; done means the menu appears for an exact command match, shows its description, and supports navigation and selection.