chore: v2.8.13 — Artifacts reinstall/edit/installs, agent steps in chat, pick a local file to attach, Windows paths as links

- Chat: an Agent step shows its task, status and tool calls and opens its conversation in place; Windows paths (E:\…, C:/…) in replies open as files
- Prompt: attach a file on this computer by path (native picker), clearer too-large messages
- Artifacts: edit title/description and a skill's files (new snapshot), Reinstall, install history, Hub-only rows, skills installed into ~/.claude/skills and ~/.agents/skills
- Files: batch upload of small files in one extract
- AI Tools: npm install falls back to --prefix ~/.local when the global prefix is not writable

server/lib/git-identity.js

@@ -866,8 +866,10 @@ async function cloneNow({ url, parent, name, once = null, partial = false }, thr
   const account = accountForDir(parent);
   const remote = remoteOf(url);
   // index-pack's delta threads: this clone's share of the cores, not all of
-  // them (clone-queue.js). Not persisted — a later fetch keeps git's default.
-  const pre = ["-c", `pack.threads=${threads}`];
+  // them (clone-queue.js) — and as many checkout workers: a tree of many
+  // small files is written one file at a time otherwise (~4x slower on 4
+  // cores). Not persisted — a later fetch or checkout keeps git's default.
+  const pre = ["-c", `pack.threads=${threads}`, "-c", `checkout.workers=${threads}`];
   const persist = [];
   const env = {};
   let restore = null;