Skill 'model:' frontmatter not applied in VS Code extension — UI shows correct model, session runs previous one

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report
• [x] I am using the latest version of Claude Code

What's Wrong?

Invoking a skill with model: opus in its frontmatter, from a fresh Sonnet session, does not switch the active inference model in the VS Code extension. The UI status indicator updates to show "Opus", but the model actually serving the request remains Sonnet (confirmed via self-report). No error or warning is shown.

This is distinct from #73881 (mid-session /model switch not applied) — here the skill is invoked at the start of a session, not via a mid-session /model command.

Steps to Reproduce

1. Claude Code VS Code extension, macOS, session started on Sonnet.
2. Create a skill with frontmatter:

---
name: test-opus
description: Test model override
model: opus
user-invocable: true
---
Say what model you are.

1. Invoke /test-opus.
2. UI status/model indicator shows "Opus".
3. Ask the model to self-report which model it is — it reports Sonnet.

What Should Happen?

The skill's model: frontmatter should switch inference to Opus for that turn (per docs: https://code.claude.com/docs/en/skills, model frontmatter field), and the UI indicator should match the model actually serving the request.

Platform

VS Code extension, macOS

Is this a regression?

Unknown