chore: stage pre-existing community tier changes

Community tier auth, backup/restore, and test updates that were already
on this branch before the telemetry sprint. Includes updated telemetry
prompt test to match 3-option community tier flow.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

bin/gstack-auth

@@ -56,11 +56,11 @@ TOKJSON
   chmod 600 "$AUTH_FILE"
 }
 
-# ─── Helper: extract JSON field (portable, no jq dependency) ─
+# ─── Helper: extract JSON field (using jq) ────────────────────
 json_field() {
   local json="$1"
   local field="$2"
-  echo "$json" | grep -o "\"${field}\":[^,}]*" | head -1 | sed "s/\"${field}\"://;s/\"//g;s/ //g"
+  echo "$json" | jq -r ".${field}" 2>/dev/null | sed 's/null//'
 }
 
 # ─── Subcommand: status ─────────────────────────────────────