release: Kun v0.2.27-2

[XingYu-Zhong]

Summary

Retry the Kun 0.2.27 release after the previous release workflow exposed cross-platform Extension native media and packaged desktop smoke failures.

Changes

• Run Windows supervised-process fixtures through the Node executable so cancellation semantics are tested instead of failing on extensionless fixture startup.
• Accept current FFmpeg filter capability flags on macOS.
• Make packaged desktop Chromium validation recover from Electron target/session replacement and execution-context navigation.
• Isolate Linux desktop smoke state and disable accessibility/credential-store interference in CI without changing production behavior.

Tests

• PR Checks typecheck and test: passed
• Linux AppImage packaged validation: passed
• macOS x64/arm64 ad-hoc packaged validation: passed
• Windows NSIS packaged validation: passed
• CodeQL: passed

Validation run: https://github.com/KunAgent/Kun/actions/runs/29607589931