v0.3.0

Cross-platform release.

• Linux (x86_64 + aarch64, static musl binaries) and Windows (x86_64) join macOS universal
• Pressure source per OS: macOS kernel level, Linux PSI (/proc/pressure/memory); Windows has no
  kernel pressure signal, so the critical-pressure rule is off there — orphan reaping, panic and
  manual kills all work (kills are immediate TerminateProcess)
• Native notifications everywhere: osascript / notify-send / PowerShell toast
• New pixel-art mascot: the TUI window watches its gauge fill and zaps the orphan-process ghost
• Confirm popup on every kill path, cursor anchored to process identity, --help exits 0