cli: V2 skill slash commands drop skill context and arguments #41245

Summary

In OpenCode V2, invoking a skill with a slash command appears to copy the
skill's SKILL.md into the prompt instead of invoking the skill itself. This
prevents the system from discovering the skill's reference files. Additionally,
arguments following the skill name are discarded.

Environment

• opencode version: v0.0.0-next-17028
• OS: Linux 6.8.0-136-generic (x86_64)
• Terminal: Ghostty, TERM=xterm-256color, COLORTERM=truecolor
• Shell: /bin/bash
• Install/channel: OpenCode V2 preview (next)
• Active plugins: None; opencode2 plugin list reports only built-in plugins

Reproduction

1. Start OpenCode V2.
2. Invoke a skill with an argument, for example:
   /skill-name This is a Test
3. Observe the prompt sent to the model and the resulting skill behavior.

Expected Behavior

The slash command should invoke the skill through the skill mechanism. The
system should load the skill instructions with access to its reference files,
and the text following the skill name (This is a Test) should be passed to
the model as the user's prompt or skill input.

Actual Behavior

The contents of SKILL.md are copied into the prompt as plain text rather than
invoking the skill. As a result, the system does not know which reference files
are available. The trailing user prompt is also lost: This is a Test does not
reach the model.

Additional Context

The behavior is consistently reproducible. The issue was observed using
OpenCode V2's slash-command skill invocation.