Fix native Runtime Pack extraction

[Open-Squilla]

Scope

• preserve legitimate case-distinct terminfo paths only for Linux-target Runtime Packs
• retain case-insensitive collision rejection for macOS and Windows targets
• remove obsolete negative 7-Zip switches while keeping pre-extraction path/link audit and post-extraction physical-tree validation
• make aggregate release auditing apply the same target-specific collision policy

Branch target

main

Linked issue

None

Release note

None; this fixes the unpublished Runtime Pack build pipeline.

Verification

• source validation
• 49 unit and workflow-contract tests
• Ruff
• Python compile check
• actionlint

Safety

Linux Runtime Packs are target-specific and may contain legitimate case-distinct terminfo entries. Other targets remain case-insensitive. On a case-insensitive filesystem, exclusive file creation still fails closed before activation.

Third-party origin

The failing entries are part of the pinned python-build-standalone CPython 3.13.15+20260814 Linux archive. Git Bash remains pinned to Git for Windows 2.55.0.windows.5.