Fall back to parent neume's facs when a neume component has none

[CThierrin]

The Liber Usualis corpus encodes @FACS on the enclosing element (one bounding box per neume figure) rather than on each individual . _get_element_zone only ever checked the itself, so every neume component in that corpus silently fell back to the (-1,-1,-1,-1) "not found" sentinel. Search results consume those coordinates directly for both the result thumbnail image and Diva's click-to-focus, so both were broken for every result on this manuscript.

Verified the fix resolves all 338,745 neume components across the full 2318-file Liber Usualis corpus (previously all -1,-1,-1,-1), with zero parse errors and no change to manuscripts that already encode facs per-component (existing fixture/tests unaffected).

Summary by CodeRabbit

• Bug Fixes

  • Improved chant notation rendering when neume components inherit positioning from their enclosing neume.
  • Prevented missing-coordinate placeholders when component-level positioning data is unavailable.
  • Preserved individual component positioning wherever it is provided.

• Tests

  • Added coverage for manuscripts using neume-level positioning data.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

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Run ID: e19513ef-349b-44cc-ad60-73568ad60dc5

📥 Commits

Reviewing files that changed from the base of the PR and between b648886 and 618fc58.

📒 Files selected for processing (2)

• app/public/cantusdata/test/core/helpers/mei_processing/test_mei_files/991961/LU-1961_0123.mei
• app/public/cantusdata/test/core/helpers/mei_processing/test_mei_parser.py

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📝 Walkthrough

Walkthrough

The MEI parser now inherits a parent neume’s zone when a component lacks its own facs reference. A new MEI fixture and regression test verify the resulting component bounding boxes.

Changes

Neume zone resolution

Layer / File(s)	Summary
Parser bounding-box resolution app/public/cantusdata/helpers/mei_processing/mei_parser.py	The parser checks a component zone first, then the enclosing neume zone. It retains the empty bounding box when neither zone provides coordinates.
MEI fixture and regression coverage app/public/cantusdata/test/core/helpers/mei_processing/test_mei_files/991961/LU-1961_0123.mei, app/public/cantusdata/test/core/helpers/mei_processing/test_mei_parser.py	The fixture adds facsimile zones and six systems of neume notation. The regression test verifies inherited component coordinates and rejects the (-1, -1, -1, -1) sentinel.

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

Merge Risk: ⚪ Minimal · up to 618fc

This change restores existing manuscript coordinates for neume components that inherit their enclosing neume’s bounding box, while preserving component-level coordinates. No actionable merge-blocking risk remains beyond normal checks and review.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 6 functions across 2 files. (1 skipped: 1…	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 and concisely describes the main change: using the parent neume's facs when a component has no facs reference.
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.

Full details: Docstring Coverage

Explanation

Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 6 functions across 2 files. (1 skipped: 1 unsupported.)

• Fix all pre-merge checks with AI

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/liber-usualis-neume-component-facs-fallback

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[CThierrin]

Resolves Issues #1006 and #1009

[etosphere]

Based on the naming convention in #987, the filename should be LU-1961_0123.mei‎.

[etosphere]

Also change the filename to LU-1961_0123.mei here.

[CThierrin]

Done, thanks