chore(main): release 3.9.1

[pplx-oss]

🤖 I have created a release beep boop

3.9.1 (2026-10-12)

What's Changed

• ci: migrate CI to Buildkite by @longlho in ci: migrate CI to Buildkite #124
• ci: isolate caches and gate releases on main Buildkite checks by @longlho in ci: isolate caches and gate releases on main Buildkite checks #126
• fix(ci): smoke-test artifacts from one cross-build by @longlho in fix(ci): smoke-test artifacts from one cross-build #127
• ci: smoke cross-built Windows worker artifacts by @longlho in ci: smoke cross-built Windows worker artifacts #128
• docs: audit guides and complete public API reference by @longlho in docs: audit guides and complete public API reference #129
• build: configure Renovate dependency updates by @longlho in build: configure Renovate dependency updates #130

Full Changelog: v3.9.0...v3.9.1

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