CLI red: backup tests, commander + env-paths deps, stub

4 tests for runBackup: full download into collection-named dirs,
incremental skip of existing files, resilient continuation after
single-file HTTP 500, and metadata.json output.

Adds commander 14.0.3 and env-paths 4.0.0 as runtime deps.

package.json

@@ -38,6 +38,8 @@
         "vitest": "2.1.9"
     },
     "dependencies": {
+        "commander": "14.0.3",
+        "env-paths": "4.0.0",
         "fast-srp-hap": "2.0.4",
         "libsodium-wrappers-sumo": "0.8.4"
     }