Show a compact top-categories summary after scans

[Muawiya-contact]

Goal

Show a compact category summary above the detailed results.

After a scan, users should quickly see where the space is coming from before expanding sections.

Suggested UI

A simple summary could look like:

Top categories
Browser cache      1.2 GB
Build artifacts    860 MB
Temporary files    220 MB

Useful helper area:

function byCategory(items) {
  const map = new Map();
  for (const f of items) {
    const key = f.category;
    if (!map.has(key)) map.set(key, []);
    map.get(key).push(f);
  }
  return [...map.entries()].sort(...);
}

Acceptance criteria

• Shows the top categories by reclaimable bytes.
• Works for both final reports and preview results.
• Does not duplicate the full row list; keep it compact.