Selecting a skill via prompt_skills keybind or Ctrl+P clears the input draft #39376

Description

When the input box already contains text (a draft prompt), selecting a skill via Ctrl+P → Skills or the prompt_skills keybind immediately invokes the skill tool and clears the existing input draft. The user's in-progress text is lost.

This is problematic for multi-skill workflows: a user writes a prompt, then wants to load a second skill (whose name they don't remember) to use alongside the first. They open the skill selector — and their draft is gone.

The problem

Selecting a skill from the selector submits a message (invokes the skill tool via session.prompt) rather than inserting /skill <name> into the input box. This means:

1. The current draft is discarded (replaced by the skill invocation message)
2. The user cannot compose /skill A + /skill B + their actual prompt in a single submission
3. There is no way to browse the skill list while preserving draft text

Expected behavior

Selecting a skill from prompt_skills (or Ctrl+P) should insert /skill <name> at the cursor position in the input box (similar to how slash-command autocomplete works in autocomplete.tsx), not submit it as a standalone message. This would let users:

• Keep their existing draft
• Compose multiple /skill invocations with their prompt before submitting
• Browse the skill list without fear of losing work

Steps to reproduce

1. Type some text in the input box (e.g., "help me refactor the auth module")
2. Press Ctrl+P → select "Skills" (or use a custom prompt_skills keybind)
3. Select any skill (e.g., "brainstorming")
4. Observed: The draft text is gone; the skill is invoked immediately as a standalone message
5. Expected: /skill brainstorming is inserted into the input, preserving the draft

Environment

• OpenCode version: 1.18.8
• OS: macOS (Darwin)
• prompt_skills keybind: custom (ctrl+s), but the issue reproduces with the default Ctrl+P path too