fix(worker): stage only resolved conflict paths in continue_merge

git add -A ran against the shared target checkout, sweeping in
whatever untracked or unrelated modified files a concurrent session
left there and committing them into an unrelated merge. Stage exactly
the paths that were reported conflicted and resolved instead.

src/ClaudeDo.Worker/Lifecycle/TaskMergeService.cs

@@ -315,7 +315,11 @@ public sealed class TaskMergeService
             if (stillConflicted.Count > 0)
                 return new MergeResult(StatusConflict, stillConflicted, "conflicts not fully resolved");
 
-            await _git.AddAllAsync(list.WorkingDir, ct);
+            // Stage exactly the resolved conflict paths — never `git add -A`, which would sweep
+            // untracked/unrelated changes left by other sessions into this merge commit (the
+            // target working dir is shared).
+            foreach (var path in unresolved)
+                await _git.AddPathAsync(list.WorkingDir, path, ct);
 
             var remaining = await _git.ListConflictedFilesAsync(list.WorkingDir, ct);
             if (remaining.Count > 0)