v2026.5.11171007

Changes:

• #646: Update release agent with explicit dev bump PR steps
• #645: Bump version to 2026.5.0-dev
• #644: Add manual validation stage to stable release pipeline
• #643: Switch stable pipeline trigger to release branches only
• #642: Narrow stable pipeline tag trigger to v* pattern
• #641: Bump version to 2026.4.0
• #639: Add release agent instructions

This list of changes was auto generated.