Took theirs for code.go and tree.html (broader UI parity pass: repo-header
partial, branches/tags counts, code/git-branch octicons, tree-panel head-
commit row, RepoTopics key, repo-about-sidebar template name).
Aligned populated.html to the new template name + wrapper class
(shithub-repo-content-grid + repo-about-sidebar).
Removed superseded internal/web/templates/repo/_about_sidebar.html — its
roles are now in internal/web/templates/_repo_about_sidebar.html (root
partial in the new structure).
