fix: address Copilot PR review comments (round 2)

- Fix init --preset error masking: distinguish "not found" from real errors
- Fix bash resolve_template: skip hidden dirs in extensions (match Python/PS)
- Fix temp dir leaks in tests: use temp_dir fixture instead of mkdtemp
- Fix self-test catalog entry: add note that it's local-only (no download_url)
- Fix Windows path issue in resolve_with_source: use Path.relative_to()
- Fix skill restore path: use project's .specify/templates/commands/ not source tree
- Add encoding="utf-8" to all file read/write in agents.py
- Update test to set up core command templates for skill restoration

scripts/bash/common.sh

@@ -213,6 +213,8 @@ except Exception:
     if [ -d "$ext_dir" ]; then
         for ext in "$ext_dir"/*/; do
             [ -d "$ext" ] || continue
+            # Skip hidden directories (e.g. .backup, .cache)
+            case "$(basename "$ext")" in .*) continue;; esac
             local candidate="$ext/templates/${template_name}.md"
             [ -f "$candidate" ] && echo "$candidate" && return 0
         done