refactor: extract git worktree parser from atlas hook

src/shared/git-worktree/parse-status-porcelain.ts

@@ -0,0 +1,25 @@
+import type { GitFileStatus } from "./types"
+
+export function parseGitStatusPorcelain(output: string): Map<string, GitFileStatus> {
+  const map = new Map<string, GitFileStatus>()
+  if (!output) return map
+
+  for (const line of output.split("\n")) {
+    if (!line) continue
+
+    const status = line.substring(0, 2).trim()
+    const filePath = line.substring(3)
+
+    if (!filePath) continue
+
+    if (status === "A" || status === "??") {
+      map.set(filePath, "added")
+    } else if (status === "D") {
+      map.set(filePath, "deleted")
+    } else {
+      map.set(filePath, "modified")
+    }
+  }
+
+  return map
+}