Fix safe_outputs failure in resolve-pull-request-review-thread test

[Copilot]

The safe_outputs job of Test Copilot Resolve Pull Request Review Thread failed because the resolve_pull_request_review_thread mutation was handed a non-node-id thread_id — a leaked GitHub REST 422 error payload — producing Could not resolve to a node with the global id.

The bad value originates in the e2e.sh fixture create_test_pr_with_review_comment: when the review-comment POST fails (e.g. 422 before the commit lands in the PR diff), the fixture could still emit a pr,comment_id,thread_id tuple with an empty/garbage identifier, which is then passed as the workflow_dispatch input consumed by the workflow's samples: block.

Changes (e2e.sh)

• Fail closed on comment creation: return an empty fixture unless the review-comment POST yields a numeric comment id, so the caller's [[ -n ... ]] guards skip the dispatch instead of triggering with a bogus id.
• Validate the resolved thread id: drop any thread_id that isn't shaped like a GraphQL node id (^[A-Za-z0-9_=-]+$), so error payloads / partial responses are never forwarded as a dispatch input.

if [[ -z "$comment_id" || ! "$comment_id" =~ ^[0-9]+$ ]]; then
    echo ""; return
fi
...
if [[ -n "$thread_id" && ! "$thread_id" =~ ^[A-Za-z0-9_=-]+$ ]]; then
    thread_id=""
fi

The test remains meaningful when the fixture succeeds; the harness can no longer dispatch the workflow with an invalid thread identifier.