fix: skip ai-superpower repo itself during project scan

apply.sh was scanning its own directory and creating a recursive .ai
symlink inside .ai/, causing infinite folder nesting in VS Code.

- Skip $SCRIPT_DIR in scan_projects() to prevent self-symlinking
- Remove incorrectly created .ai/.ai symlink and .ai/.gitignore
- Add -root session reset command to ai-root-instructions.md
- Document -root command in README

.ai/.gitignore

@@ -1 +0,0 @@
-.ai

apply.sh

@@ -180,6 +180,7 @@ scan_projects() {
   while IFS= read -r gitdir; do
     project="$(cd "$(dirname "$gitdir")" && pwd)"
     if [[ -f "$project/.ai-superpower" ]]; then continue; fi
+    if [[ "$project" == "$SCRIPT_DIR" ]]; then continue; fi
     setup_project "$project"
     (( projects_found++ )) || true
   done < <(find "$dev_root" -mindepth 2 -maxdepth 4 -name ".git" -type d 2>/dev/null || true)