Reclaimable total counts duplicated cache files twice

[Muawiya-contact]

report::build computes:

let total_reclaimable = findings.iter().map(|f| f.reclaimable).sum::<u64>()
    + duplicate_sets.iter().map(|d| d.wasted).sum::<u64>();

A file can be in both halves. Two identical 1 GB installers under /tmp/ give two findings at 1 GB each plus a duplicate set with 1 GB wasted — headline says 3 GB where at most 2 GB is actually reclaimable.

Related: find_duplicates runs over every entry including ones that classify as protected, so system files can contribute wasted bytes to a total the user is never allowed to act on.

crates/diskern-core/src/report.rs:53