fix: refactor forest-cli snapshot command

[hanabi1224]

Summary of changes

On top of #7249 and #7254

Changes introduced in this pull request:

• move file manipulation logic from cli to server
• add CI test to ensure export command is kill-resilient
• update snapshot checksum file extension from forest.car.sha256sum to forest.car.zst.sha256sum

Reference issue to close (if applicable)

Closes

Other information and links

Change checklist

• I have performed a self-review of my own code,
• I have made corresponding changes to the documentation. All new code adheres to the team's documentation standards,
• I have added tests that prove my fix is effective or that my feature works (if possible),
• I have made sure the CHANGELOG is up-to-date. All user-facing changes should be reflected in this document.

Outside contributions

• I have read and agree to the CONTRIBUTING document.
• I have read and agree to the AI Policy document. I understand that failure to comply with the guidelines will lead to rejection of the pull request.

Summary by CodeRabbit

• New Features
  • Snapshot and snapshot-diff exports now run asynchronously with clearer completion vs cancellation messaging and improved progress handling.
  • Export-diff now returns explicit done/cancelled outcomes for more consistent CLI results.
• Bug Fixes
  • Prevents concurrent snapshot export jobs and overlapping diff ranges from starting.
  • Cancellation and export-status waiting are more reliable, and successful exports now generate checksum sidecar files.
• Tests
  • Updated snapshot export/diff checks to verify async state transitions, cancellation behavior, and concurrency protections.

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Walkthrough

Snapshot export now runs in detached RPC tasks with temp-file persistence and checksum sidecars, while the CLI and calibnet scripts update to poll, cancel, and verify export concurrency state.

Changes

Detached Export Execution and Concurrency

Layer / File(s)	Summary
Path helpers and export result shape src/db/car/forest.rs, src/rpc/types/mod.rs	Adds temp and checksum path helpers and changes ApiExportResult::Done to a unit variant.
Detached chain export RPC handling src/rpc/methods/chain.rs, src/ipld/util.rs	Updates ForestChainExport::handle and ForestChainExportDiff::handle to run in detached tasks with temp paths, checksum-sidecar writing, anyhow::ensure! depth validation, and ApiExportResult cancellation handling.
Diff export store threading src/tool/subcommands/archive_cmd.rs	Changes the diff export branch in do_export to pass store.shallow_clone() directly into stream_chain.
Snapshot CLI export flow updates src/cli/subcommands/snapshot_cmd.rs, src/lib.rs	Makes snapshot export paths absolute, removes client-side persistence and checksum writing, switches byte tracking to the temp export path helper, changes export-status --wait termination, uses a cancellation token in export-diff progress handling, and re-exports FutureExt in the crate prelude.
Calibnet export concurrency checks scripts/tests/calibnet_export_check.sh, scripts/tests/calibnet_export_diff_check.sh	Updates the calibnet export scripts to run exports in the background, poll export status, verify cancellation state, reject overlapping export requests, and confirm the original export still completes after the CLI process is killed.

Estimated code review effort: 4 (Complex) | ~60 minutes

Possibly related PRs

• ChainSafe/forest#7249: Introduces ChainExportGuard-based locking and cancellation in the RPC chain export flow that this PR builds directly upon.
• ChainSafe/forest#6128: Adds export-status and export-cancel CLI/RPC plumbing and changes export-result/status handling that this PR extends.
• ChainSafe/forest#6074: Touches snapshot export-diff end-to-end across snapshot_cmd.rs, chain.rs, and rpc/types/mod.rs — the same files this PR modifies.

Suggested labels:RPC

Suggested reviewers:akaladarshi, LesnyRumcajs, sudo-shashank

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 16.67% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: a refactor of the forest-cli snapshot command.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch hm/refactor-cli-snapshot-cmd

✨ Simplify code

• Create PR with simplified code
• Commit simplified code in branch hm/refactor-cli-snapshot-cmd

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[LesnyRumcajs]

update snapshot checksum file extension from forest.car.sha256sum to forest.car.zst.sha256sum

That's a breaking change, no?

[LesnyRumcajs]

no green checkmark, no review!