v0.5.3

Changelog

• 3c13fbd Whole-repo audit: image ambiguity, gzip trailer, fd leak, singleflight, and style fixes
• 3706a65 fix(os-image): pull scrcpy-rfb from its own repo's master release (#136)
• 8b18266 fix: harden cocoon for sub-1500-MTU / high-vCPU cloud hosts (CH rlimits + CNI MTU/MSS) (#135)