fix(labels): use gh jq for paginated label reads

[ss-o]

Summary

• replace the dry-run helper's gh api --template usage with gh api --jq '.[]'
• keeps paginated label reads as newline-delimited JSON objects
• fixes compatibility with the installed gh version, where the template json function is unavailable

Test Plan

• ruby -c scripts/labels-dry-run.rb
• scripts/labels-dry-run.rb --repo z-shell/.github --include-clean
• scripts/labels-dry-run.rb --repo z-shell/zi
• scripts/labels-dry-run.rb --repo z-shell/.github --json | ruby -rjson -e 'data=JSON.parse($stdin.read); puts "repos=#{data["repos_scanned"]} drift=#{data["repos_with_drift"]}"'
• scripts/labels-dry-run.rb --repo z-shell/.github --all-repos exits 2

Follow-up for #411 and #423.

[Copilot]

Pull request overview

This PR updates the label audit dry-run script to use gh api --jq instead of --template, aiming to preserve paginated label reads as newline-delimited JSON while restoring compatibility with GitHub CLI versions that don’t support the template json function.

Changes:

• Replaced gh api --template output formatting with gh api --jq '.[]' for paginated label listing.
• Kept the script’s paginated label read path intended to produce newline-delimited JSON objects for downstream parsing.