Extract BlameColumnResizer from blame_info.vue

Joseph Fletcherrequested to merge
extract-blame-column-resizer into master

What does this MR do and why?

Extracts the drag handle, width persistence, and breakpoint behaviour from blame_info.vue into a new standalone blame_column_resizer.vue component.

This is a pure refactor — no visual or behavioural change. It is a prerequisite for !247210 (closed), which uses BlameColumnResizer in the chunked grid path as well.

Changes

constants.js

  • Adds BLAME_AGE_COLORS, BLAME_COLUMN_DEFAULT_WIDTH, BLAME_COLUMN_MAX_WIDTH, BLAME_COLUMN_MIN_WIDTH, and BLAME_COLUMN_WIDTH_STORAGE_KEY so both viewer paths can share them.

blame_column_resizer.vue (new)

  • Owns the AccessiblePanelResizer wiring, PanelBreakpointInstance listener, and localStorage persistence.
  • The caller keeps the resulting width via v-model because only the caller knows how to apply it (container width vs. grid track).

blame_info.vue

  • Drops ~50 lines of resizer logic.
  • Replaces the inline <accessible-panel-resizer> with <blame-column-resizer v-model="containerWidth" />.

Tests

  • blame_column_resizer_spec.js (new) — full coverage of the extracted component.
  • blame_info_spec.js — trimmed to only assert the width is applied correctly; breakpoint/persistence tests moved to the new spec.

Checklist

  • blame_info.vue behaviour is unchanged
  • BlameColumnResizer handles desktop/mobile breakpoint correctly
  • Width is persisted to and restored from localStorage
  • Drag handle is hidden on non-desktop viewports

Merge request reports