fix: correct compress() density docstring to kg/m³

[PythonFZ]

Summary

molify.compress's docstring documented its density argument as g/cm³, but the function passes that value straight to calculate_box_dimensions, which expects kg/m³ — the same convention already used by pack and calculate_density. A user trusting the docstring would pass 1.0 for water (1 g/cm³) and get a box 1000× too sparse.

The runtime logic was already correct and consistent with the rest of the package; only the docstring was wrong. This standardizes compress on the package-wide kg/m³ convention by fixing the one misleading line.

     density : float
-        The target density in g/cm^3.
+        The target density in kg/m^3.

Verification (TDD)

The existing test_compress / test_compress_freeze already pin the kg/m³ contract. To confirm they genuinely guard it, I temporarily applied the naive density * 1000 "fix":

• RED: both tests fail (calculate_density → ~1,000,000 instead of 1000).
• GREEN: with the unmodified (correct) logic, all 454 tests pass.

This demonstrates the kg/m³ contract is real and tested, so the docstring correction now matches verified behavior.

Test Plan

• uv run pytest → 454 passed
• Confirmed the rejected ×1000 conversion breaks the suite (RED), proving the contract is guarded

🤖 Generated with Claude Code

Summary by CodeRabbit

• Documentation
  • Clarified the documented density units for compression to use kg/m³ instead of g/cm³.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: a391b7b8-3636-415e-8cec-43f6947b5303

📥 Commits

Reviewing files that changed from the base of the PR and between 32422e3 and e6be7c5.

📒 Files selected for processing (1)

• src/molify/compress.py

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📝 Walkthrough

Walkthrough

The density parameter unit in the compress() function's docstring is corrected from g/cm^3 to kg/m^3. No logic or behavior is changed.

Changes

Docstring Unit Correction

Layer / File(s)	Summary
Fix density unit in compress() docstring src/molify/compress.py	Docstring unit for density parameter updated from g/cm^3 to kg/m^3.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~1 minutes

Poem

A unit was wrong, a small typo astray,
kg/m^3 is the proper display.
The bunny hopped in, corrected the text,
No logic was harmed — what could come next?
🐇✨

🚥 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 accurately summarizes the docstring fix for compress() density units and matches the main change.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
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/compress-density-unit-docstring

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