v2026.5.11171008

Changes:

• #527: Update release agent with explicit dev bump PR steps
• #526: Bump version to 2026.5.0-dev
• #525: Add manual validation stage to stable release pipeline
• #524: Switch stable pipeline trigger to release branches only
• #523: Narrow stable pipeline tag trigger to v* pattern
• #522: Bump version to 2026.4.0
• #521: Add release agent instructions

This list of changes was auto generated.