Fix test data: dynamic owner check and missing PR number

- issue-1195: compare env.variable against github.repository_owner
  instead of hardcoded 'actions-oss'
- pull-request: add missing "number" field to event.json to prevent
  %!f(<nil>) in github.ref

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pkg/runner/testdata/pull-request/event.json

@@ -1,4 +1,5 @@
 {
+  "number": 1,
   "pull_request": {
     "head": {
       "ref": "sample-head-ref"