Implement project milestone allocation strategy (v1.0+)

[ashleyshaw]

Summary

Implement automated version-based milestone allocation and project routing for issues and PRs.

Scope

1. Version Milestone Lifecycle — Create milestones for v1.0 through v1.6
2. Milestone Allocation — Assign issue Epic: Multi-Provider Agent Standardization Initiative #1079, child issues, related PRs to v1.0; assign recent issues (last 2 weeks) to v1.0
3. Project Routes Configuration — Create .github/project-routes.yml to route all .github issues to GitHub Project 33
4. Workflow Enhancement — Extend metadata-governance.yml to:
   • Read milestone strategy from config
   • Auto-allocate new issues to appropriate version milestone
   • Warn when milestone approaches capacity
5. Safeguards — Ensure only finite, release-managed milestones are created (no per-issue milestones)

Definition of Ready

• Strategy confirmed: version-based + epic labels
• Milestones identified: v1.0–v1.6
• Project target: lightspeedwp/projects/33
• Branch created: feat/project-milestone-allocation-strategy

Definition of Done

• v1.0–v1.6 milestones created
• Issue Epic: Multi-Provider Agent Standardization Initiative #1079 + children + related PRs assigned to v1.0
• Recent issues (2-week window) assigned to v1.0
• .github/project-routes.yml created and documented
• metadata-governance.yml extended with milestone logic
• Workflow passes all CI checks
• Code review feedback from CodeRabbit/Gemini addressed
• PR merged to develop

[linear-code]

LS-1681

[github-actions]

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