Release v0.28.6

What's Changed

• fix(slack): preserve access to oversized attachments by @cpacker in #3345
• chore: add channels code owners by @just-cameron in #3346
• fix(local): isolate conversation model token settings by @cpacker in #3353
• fix(local): preserve provider length stop reasons by @cpacker in #3354
• fix(local): stop treating output limits as context overflow by @cpacker in #3355
• fix(listener): publish authoritative executing tool ids on loop state [LET-9640] by @cpacker in #3352
• fix: expose app-server websocket disconnects by @sarahwooders in #3358
• fix: enforce send-boundary image normalization [LET-9618] by @cpacker in #3357
• feat: tag onboarding-created agents [LET-9625] by @cpacker in #3356
• chore: bump version to 0.28.6 by @github-actions[bot] in #3351

Full Changelog: v0.28.5...v0.28.6