ci(skit): test-gpu condition may not work as intended inside workflow_call

[staging-devin-ai-integration]

Problem

The test-gpu job in skit.yml has:

if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository

Since skit.yml is triggered via workflow_call from ci.yml, github.event_name in the called workflow is workflow_call rather than the original event name. This means github.event_name != 'pull_request' is always true, so GPU tests would run for fork PRs too (the condition was meant to skip them for security reasons — self-hosted runners shouldn't execute untrusted code).

Suggested fix

Pass the original event name as an input to the reusable workflow, or use github.event.pull_request existence check instead:

if: github.event.pull_request == null || github.event.pull_request.head.repo.full_name == github.repository

Context

This is a pre-existing issue — skit.yml was already a workflow_call target before #295. Surfaced by Devin Review during CI consolidation.