fix(ci): gh pr create doesn't support --json flag

[ethernet8023]

What does this PR do?

The js-autofix workflow (merged in #65186) uses gh pr create --json number --jq '.number' to capture the PR number, but gh pr create doesn't support
the --json flag — every workflow run fails with unknown flag: --json.

Extract the PR number from the URL that gh pr create prints to stdout
instead (format: https://github.com/<org>/<repo>/pull/<number>).

Related Issue

Follow-up fix for the workflow merged in #65186.

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)

Changes Made

• .github/workflows/js-autofix.yml: replaced gh pr create --json number --jq '.number' with PR_URL=$(gh pr create ...) + PR_NUM=$(echo "$PR_URL" | grep -oE '[0-9]+$')

How to Test

1. Merge this PR.
2. Trigger the auto-fix lint issues & formatting workflow (push a JS file with a fixable lint issue to main, or workflow_dispatch).
3. The apply-patch job should successfully create a PR on bot/js-autofix instead of failing with unknown flag: --json.

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass — N/A: CI workflow change, no Python tests affected
• I've added tests for my changes — N/A: GitHub Actions workflow, validated via YAML parse + structure check
• I've tested on my platform: NixOS (workflow YAML validated with yaml.safe_load)

Documentation & Housekeeping

• I've updated relevant documentation — N/A (workflow internal)
• I've updated cli-config.yaml.example if I added/changed config keys — N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — N/A
• I've considered cross-platform impact — N/A (GitHub Actions only)
• I've updated tool descriptions/schemas if I changed tool behavior — N/A

Screenshots / Logs

Failing run after #65186 merged:

Apply patch	Create/update PR and enable auto-merge	unknown flag: --json
Apply patch	Create/update PR and enable auto-merge	Usage:  gh pr create [flags]
Apply patch	Create/update PR and enable auto-merge	##[error]Process completed with exit code 1.