fix(archive,paste): make symlinks survive compress / extract / copy

[lovehunter9]

Summary

Make symbolic links behave sensibly across archive and copy operations:

• Compress: directory symlinks are staged (via cp -a -l) so 7z stores them as links instead of erroring with errno=22; PreserveSymlinks now also applies to tar.gz/bz2/xz; when not preserving, sources are dereferenced; same-name sources are rejected up front with a clear message instead of a raw 7z "Duplicate filename" failure.
• Extract: undo 7z's absolute-symlink confinement (it prepends the output dir to the target) so a preserved absolute link keeps its original target; and a symlink 7z refuses as "Dangerous link path" no longer fails the whole extract — the unsafe link is skipped and the rest extracts normally.
• Copy: drop rsync --safe-links (it silently dropped absolute / out-of-tree links) and chown links with lchown (so a dangling link no longer ENOENTs); CheckPathExists now treats a dangling symlink as existing so it can be copied/extracted.

Notes

• Tree-escaping symlinks are still confined by the tools' zip-slip protections; faithfully materializing them would require a read/share-side containment guard (tracked separately).

Test plan

• Compress a folder containing a directory symlink with preserve on (zip / 7z / tar.gz) → succeeds, link stored.
• Compress with two same-name sources → clear "would both be archived as" error.
• Compress an absolute file symlink, extract → link keeps its original target.
• Extract an archive whose only/one entry is an escaping symlink → no hard failure.
• Copy a dangling symlink → no chown ENOENT, link copied.
• Regression: normal files/folders compress, extract and copy unchanged.

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