chore(main): release 4.6.0

[github-actions]

🤖 I have created a release beep boop

4.6.0 (2026-05-09)

Features

• webhooks: public to_wire_dict() serialization seam (#602) (6a06e88)

Bug Fixes

• decisioning: re-validate params through platform method's stricter subclass annotation (#597) (3d269f5)
• webhooks: add canceled/rejected/auth-required to A2A status map; fail fast on unknowns (#606) (89f9491)
• webhooks: correct type annotations for extract_webhook_result_data and payload builders (#600) (e624b5c)
• webhooks: reject unknown AdCP status in create_a2a_webhook_payload (#605) (37d2cda)

Documentation

• contributing: document PR title format to prevent silent CHANGELOG drops (#580) (2c5ec64)

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[github-actions]

🤖 Created releases:

• v4.6.0

🌻