fix(labels): support older Ruby hash iteration

[ss-o]

Summary

Fixes the label sync audit script used by the #411 label-taxonomy rollout.

On the local Ruby available in this maintainer environment, Hash#filter_map is unavailable, so the documented dry-run command failed before it could audit labels. This changes the two hash filter_map call sites to each_with_object([]) while preserving the same output shape.

Verification

• ruby -c scripts/labels-sync.rb
• ruby -e 'require "yaml"; data=YAML.safe_load(File.read("lib/labels.yml"), aliases: false); names=data.fetch("labels").map{|l| l.fetch("name")}; abort "duplicate labels" unless names.uniq == names; puts "labels=#{names.size} legacy=#{data.fetch("legacy_migrations").size}"'
• scripts/labels-sync.rb --repo z-shell/.github --include-clean
  • Read-only dry run.
  • Canonical labels: 31.
  • Legacy migrations: 30.
  • Repos scanned: 1.
  • Repos with drift: 0.
  • z-shell/.github clean.

Related

Refs #411.

Agent handoff

No handoff needed.

[Copilot]

Pull request overview

This pull request updates the label sync audit script used during the label taxonomy rollout to run on older Ruby versions by removing usage of Hash#filter_map, which is unavailable in the maintainer environment.

Changes:

• Replaced two Hash#filter_map call sites with each_with_object([]) to preserve output shape while restoring compatibility.
• Kept the resulting updates and legacy_present arrays identical in structure for downstream sorting and summaries.