fix(inventory): make change hash order invariant

[ooolafhu]

Description

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

Summary by CodeRabbit

• Bug Fixes
  • Improved inventory signature stability by deterministically ordering set-like fields and nested resource lists before hashing.
  • Real content changes (for example, GPU identifiers or block device parent details) still update the signature, while parent ordering changes behave as expected.
  • Added clearer error behavior for nil inventory snapshots.
• Tests
  • Expanded coverage to ensure reordering does not change the computed hash (and does not mutate the original snapshot), validates detection of meaningful item changes, and confirms proper handling of nil input.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: 12dc5877-3627-4a43-b267-acba149c3b62

📥 Commits

Reviewing files that changed from the base of the PR and between ef434c7 and 374734b.

📒 Files selected for processing (2)

• internal/inventory/hash.go
• internal/inventory/hash_test.go

🚧 Files skipped from review as they are similar to previous changes (2)

• internal/inventory/hash.go
• internal/inventory/hash_test.go

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📝 Walkthrough

Walkthrough

ComputeHash now canonicalizes unordered component and resource collections before hashing. Tests verify order independence, input immutability, content sensitivity, parent ordering, and nil snapshot errors.

Changes

Inventory hashing

Layer / File(s)	Summary
Canonicalize inventory fields internal/inventory/hash.go	ComputeHash sorts component lists and canonicalizes GPU, block device, and NIC interface slices using stable JSON ordering, with helpers and error handling.
Validate hash stability and sensitivity internal/inventory/hash_test.go	Tests verify reordered set-like fields produce equal hashes without mutation, while item changes, parent ordering, and nil snapshots produce the expected results.

Estimated code review effort: 3 (Moderate) | ~20 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 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: making inventory change hashing order-invariant.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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 docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/compute-hash-sort

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