feat(cli): append-only artifact store — bin/ and wit/ never deleted

[joshuajbouw]

Linked Issue

Closes #578

Summary

Content-addressed artifacts in bin/ and wit/ are never auto-deleted on capsule remove. The audit chain records BLAKE3 hashes that must always resolve to real binaries. Deleting artifacts breaks provability.

Changes

• Remove cleanup_wasm_binary() function (was called on capsule remove)
• Remove cleanup_wit_files() function (was called on capsule remove)
• capsule remove now only deletes the capsule directory (metadata, Capsule.toml, config)
• Artifacts are append-only by default
• CHANGELOG.md updated

This is the Nix model: append-only store, explicit garbage collection. Future astrid gc command for operator-initiated purge with confirmation and audit entry.

Test Plan

• 8 remove tests pass
• 149 total tests pass
• cargo clippy -p astrid -- -D warnings clean

Checklist

• Linked to an issue
• CHANGELOG.md updated under [Unreleased]

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request fundamentally changes the artifact storage policy to an append-only model, ensuring that content-addressed binaries and WIT files are never automatically removed. This change is crucial for maintaining the integrity of the audit chain, as deleting these artifacts would compromise provability. Consequently, the capsule remove command's scope has been narrowed to only remove capsule-specific metadata, with future plans for a dedicated garbage collection utility.

Highlights

• Artifact Storage Policy: Content-addressed artifacts in bin/ and wit/ directories are now append-only and will never be automatically deleted during capsule removal to maintain the audit trail and provability.
• Capsule Removal Behavior: The capsule remove command now exclusively deletes the capsule's metadata directory (containing Capsule.toml and configuration), no longer attempting to clean up associated WASM binaries or WIT files.
• Code Simplification: The cleanup_wasm_binary() and cleanup_wit_files() functions, previously responsible for artifact deletion, have been removed.
• Future Cleanup Mechanism: A future astrid gc command is planned for explicit, operator-initiated garbage collection of artifacts, aligning with the Nix model.
• Documentation: The CHANGELOG.md has been updated to reflect the new append-only artifact store policy.

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Artifacts now stay, Audit trail, forever true, No more auto-delete.

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[gemini-code-assist]

Code Review

This pull request successfully implements an append-only artifact store for bin/ and wit/ directories, ensuring that content-addressed artifacts are never automatically deleted during capsule removal. This change is well-justified by the need to maintain an audit trail and provability of binaries, aligning with the Nix model for artifact management. The removal of cleanup_wasm_binary() and cleanup_wit_files() simplifies the remove_capsule logic, and the updated CHANGELOG.md clearly documents this architectural shift. The implementation is clean and directly addresses the stated goal.