v0.1.0-rc.9

What's Changed

• node: tell agents to propose installing the a2a CLI by @kaisoz in #570
• feat(auth,sts,egress): task-scoped Biscuit attenuation, two-token STS, and egress brokers by @aojea in #578
• v0.1.0 readiness: release pipeline, operator-plane proto contract, storage units, SDK parity by @aojea in #589
• fix: pre-GA security, conformance, release, and test-pyramid hardening by @aojea in #590

Full Changelog: v0.1.0-rc.8...v0.1.0-rc.9