feat: flag vendored clones and make the repo filter navigable

Two Repos-tab quality-of-life changes:

- External/vendored clones (repos with zero of your own commits — e.g. an
  upstream cloned for reference and never pushed to) are measured on
  refresh, cached in stats_cache (RepoStatsEntry.authored), shown with a
  dim ⧉ marker prefixed to the name, and hidden by the persistent
  hide_external_clones config toggle (key `x`, the `S` menu, or
  `vulp list --external|--no-external`). A fork you do commit to stays
  yours, so only true reference clones are flagged.

- Inside the `/` filter box, ↑↓ now move through the live-filtered
  results and Enter opens the highlighted repo/project directly, instead
  of the filter only "locking" on Enter with no way to scroll or select.

src/hub/modals_spawn.rs

@@ -859,10 +859,12 @@ pub fn spawn_api_refresh(state: &mut HubState) {
             // network, cheap (~0.2s/50 repos measured), so a plain sequential
             // pass is fine. Only run during `[R]`, never on tab entry.
             let _ = tx.send(RefreshMsg::Progress("Measuring release cadence + repo size...".into()));
+            let matcher = crate::stats::OwnEmailMatcher::resolve(&cfg, &accounts);
             let mut stats_cache = crate::stats::cache::load();
             for (name, path) in &repo_paths {
                 let size = crate::stats::size::repo_size(path);
                 stats_cache.record_size(name, size.git_kb, size.tree_kb);
+                stats_cache.record_authored(name, crate::stats::has_own_commit(path, &matcher));
             }
             let _ = crate::stats::cache::save(&stats_cache);