PR Stack Template

PR description should include these fields:

• Depends-on: PR-1-id | none
• Stack-Layer: L1 | L2 | L3 | L4 (maps to capabilities, work packages, tasks, deliverables)
• Release-Channel: alpha | beta | rc | canary | release
• State: optional override when lifecycle differs from release channel
• Rollback-Plan: command or rollback branch
• Compatibility: BREAKING | NON_BREAKING
• API-Shape-Impact: none | additive | breaking
• Validation: lint, test, migration check with command list

If API-Shape-Impact is breaking:

• child PRs that compile against this API cannot merge first.