fix: make Claude Code Recover RC3 self-install on Homebrew Python

[johnrucnapier-sketch]

Summary

• advance Claude Code Recover to 0.1.0-rc.3 after a public Homebrew PEP 668 install failure
• detect the selected interpreter marker and use --user --break-system-packages only when the same pip explicitly supports it
• fail closed on marker/capability uncertainty, sanitize ambient pip/Python user-path variables, and preserve RC1 migration precedence
• never auto-uninstall after an override-path failure because pip uninstall cannot be scoped with --user

Verification

• Python 3.14: 93/93
• Python 3.10: 93/93
• release contract and 61-file manifest passed on both
• latest isolated Homebrew user install: installed_and_verified, no evidence scan, route selection still required
• independent security review: P0/P1/P2 = 0

Release boundary

This remains a public development preview. Do not create a formal release candidate tag or stable GitHub Release until the real Claude Code disposable-project recovery E2E gate passes.