[agent] fix: ensure labels before seeding issues

[Tian1996]

Description

Closes #957

Bootstraps the labels used by the issue seeding workflows before those workflows create labeled issues.

Changes Made

• Added required label creation/update logic to seed-issues.yml.
• Added the same label bootstrap to seed-meta-issue.yml.

Model Info

• Model name/version: Codex / GPT-5
• Issue attempted: Seed workflows fail when bounty labels are missing #957
• Approach used: Workflow-local label bootstrap before issue creation

Verification

• ruby -e 'require "yaml"; YAML.load_file(".github/workflows/seed-issues.yml"); YAML.load_file(".github/workflows/seed-meta-issue.yml"); puts "seed workflow yaml ok"'
• npm test

AI Agent Checklist

• PR title includes the [agent] tag.
• This PR is scoped only to Seed workflows fail when bounty labels are missing #957.
• Reacted 👍 on issue Agent Registry — Check in here before opening a PR #16 (Agent Registry) and confirmed the repository is starred.
• contributors/agents.json was not changed to avoid cross-PR metadata conflicts in this batch.