Align GitHub Activity timeline columns

[brsbl]

Summary

• Moves Activity immediately before From so the row reads Resource, Repo, Activity, From.
• Lets the desktop From layout span its full cell so the updated time aligns with the table's right content edge.
• Preserves the existing compact inline timestamp when desktop columns collapse.

Visual evidence

Both screenshots use the same real BB dev app, cached three-item GitHub result set, 1440x900 viewport, and window bounds.

Before	After

Responsive branch evidence: 1100x760 and 768x760.

Validation

• npm run check --workspace=bb-plugin-github-notifications — 3 files, 47 tests
• Tests assert header and cell order, Activity adjacency to From, right-edge desktop time layout, and responsive inline ownership
• Real BB dev app at 1440, 1100, and 768 px widths
• git diff --check

BB-Thread-ID: thr_bwikffmsvp