Agent Skills: branch-tombs

Builds a branch graveyard for a git repository. Reads every local and remote branch, records who last touched it and when, computes age, ahead/behind, and whether it is merged into the trunk, then renders a light-theme website that shows the stale branches as headstones and lists the ones that are safe to delete. Use when the user runs /branch-tombs or asks about stale, dead, abandoned, or old branches, branch cleanup, or which branches are safe to prune.