abc9a8f292
git stash pop without --index restores stashed staged changes as unstaged. When a nested repo had staged WIP before the isolated agent ran, the pop in applyNestedPatches() brought the content back but lost the user's index state.
Pass { index: true } so pop uses --index, matching the root merge path that already does the same thing.
Added a regression test that stages a pre-existing edit in the nested repo, runs applyNestedPatches, and asserts the file is still in the index (porcelain "M " with the trailing space) and the cached diff still shows the staged WIP.
Fixes #3196