release: v0.6.1

[bug-ops]

Summary

• Bump version from 0.6.0 to 0.6.1 across all workspace manifests (Cargo.toml, Cargo.lock, exarch-python's pyproject.toml, exarch-node's package.json) plus the exarch-cli skill metadata
• Finalize CHANGELOG.md's [0.6.1] section: reviewed every commit since v0.6.0 and added the missing sevenz-rust2 0.21.5 -> 0.22.2 dependency-bump entry
• Consolidated the changelog's [0.5.0] section, which had duplicate ### Added and ### Fixed headers from past edits, into a single instance of each
• Fixed two broken rustdoc intra-doc links (std::io::Error::other) that failed the --deny rustdoc::broken_intra_doc_links gate
• Updated README.md and crates/exarch-core/README.md to document the six additional #[non_exhaustive] enums landing in this release (ArchiveError, QuotaResource, ArchiveType, CompressionCodec, IssueCategory, EntryType)

Checklist

• Version updated in all manifests
• CHANGELOG.md has release section with date
• README reflects new version
• All CI checks pass locally (fmt, clippy, nextest, doc-tests, rustdoc gate, cargo deny advisories)
• Ready for tagging after merge