OpenConceptLab/ocl_issues#2574 | Polish collection reference displays

[schultzjack]

Linked Issue

Closes OpenConceptLab/ocl_issues#2574

Summary

• Moves the source-group expand/collapse control to the left of the checkbox column so grouped references read as a hierarchy instead of a flat list.
• Updates the references Results column to use the same concept/mapping icon + count pattern used elsewhere in the UI.
• Aligns the Versions + Expansions concept/mapping count columns by sharing the same count/action column widths between version rows and expansion rows.

Test Plan

• npm ci --ignore-scripts
• ./node_modules/.bin/eslint src/components/references/ReferenceSourceGroupedResults.jsx src/components/repos/CollectionVersionsTab.jsx
• NODE_ENV=production npm run build — attempted, but the local build is blocked by the existing node-sass@4.14.1 runtime incompatibility on macOS arm64 / Node v25 (Unsupported runtime (141)). Webpack reached compilation and failed in Sass loader for existing SCSS/CSS imports, not in the touched JSX files.

Notes

I kept this PR scoped to the three display polish items in #2574; it does not change reference data fetching or expansion behavior.