feat(cli): atomic publish + aliasing checks on decompress

[polaz]

Summary

Mirror the compress hardening (#45) onto the decompress command in cli/src/main.rs:

• ensure_distinct_paths gates the call before any I/O — identical or hard-linked input/output paths are rejected so the decoder cannot overwrite its own source mid-stream.
• ensure_regular_output_destination pre-flights the destination so a directory or non-regular entry fails fast (no scratch file is created on this reject path).
• Decoded bytes stream into a scratch file via create_temporary_output_file; replace_output_file promotes it to the final destination only after a fully successful decode.
• Decoder/copy/metadata errors remove the scratch file so partial state never lands at the final path.

Test plan

6 new tests in cli/src/main.rs::tests — nextest 20/20 pass, lint + check clean.

• decompress_rejects_same_input_and_output_paths
• decompress_rejects_hardlinked_output_paths (unix only)
• decompress_reports_open_error_for_missing_input — also asserts the destination is not created
• decompress_rejects_non_regular_output_before_creating_temp_file — also asserts no .tmp. scratch lands
• decompress_cleans_temp_file_on_decode_failure — garbage bytes in, scratch removed, no final file
• decompress_roundtrips_known_content — happy-path sanity

Closes #46.

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ℹ️ Review info

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📥 Commits

Reviewing files that changed from the base of the PR and between ee9f8ca and 76267a8.

📒 Files selected for processing (1)

• cli/src/main.rs

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/#46-cli-decompress-atomic

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[Copilot]

Pull request overview

This PR mirrors the CLI compress hardening from #45 onto decompress in cli/src/main.rs, adding aliasing checks and an atomic temp-file publish flow so decompression can’t overwrite its own input and never leaves partial output behind.

Changes:

• Add ensure_distinct_paths + ensure_regular_output_destination preflight to decompress() before any I/O.
• Write decompressed bytes to a scratch file (create_temporary_output_file) and promote via replace_output_file only after successful decode.
• Add decompression-focused tests covering aliasing rejection, preflight behavior, temp-file cleanup on failure, and a roundtrip sanity case.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.