refactor: extract git worktree parser from atlas hook

src/shared/git-worktree/parse-diff-numstat.ts

@@ -0,0 +1,27 @@
+import type { GitFileStat, GitFileStatus } from "./types"
+
+export function parseGitDiffNumstat(
+  output: string,
+  statusMap: Map<string, GitFileStatus>
+): GitFileStat[] {
+  if (!output) return []
+
+  const stats: GitFileStat[] = []
+  for (const line of output.split("\n")) {
+    const parts = line.split("\t")
+    if (parts.length < 3) continue
+
+    const [addedStr, removedStr, path] = parts
+    const added = addedStr === "-" ? 0 : parseInt(addedStr, 10)
+    const removed = removedStr === "-" ? 0 : parseInt(removedStr, 10)
+
+    stats.push({
+      path,
+      added,
+      removed,
+      status: statusMap.get(path) ?? "modified",
+    })
+  }
+
+  return stats
+}