fix: strip wrapper command line from stackql output before jq parsing

The wrapper prints the binary path + args as the first line of output,
which is not JSON. grep -E '^\s*[\[{]' keeps only lines that are actual
JSON, discarding both that command line and any leftover blank lines.

https://claude.ai/code/session_01Y8NseCm28GqE8nQ1Yvg5aa

Author: claude

.github/workflows/setup-stackql-test.yml

@@ -35,11 +35,11 @@ jobs:
         echo "Registry list output:"
         echo "$OUTPUT"
 
-        # When the wrapper is active, @actions/exec writes stackql's stdout directly to the
-        # wrapper process's stdout, and core.debug() appends ::debug:: annotations immediately
-        # after (on the same line, since the JSON has no trailing newline). Strip all GitHub
-        # Actions workflow commands (::name::value) before handing the output to jq.
-        CLEAN_JSON=$(echo "$OUTPUT" | sed 's/::[a-z-]*::.*$//' | grep -v '^[[:space:]]*$')
+        # When the wrapper is active, @actions/exec also prints the command line before the
+        # output, and core.debug() appends ::debug:: annotations immediately after the JSON
+        # (on the same line, since the JSON has no trailing newline). Strip workflow commands
+        # and then keep only lines that look like JSON (starting with [ or {).
+        CLEAN_JSON=$(echo "$OUTPUT" | sed 's/::[a-z-]*::.*$//' | grep -E '^\s*[\[{]')
 
         # Validate JSON structure: array of objects each with provider and version keys
         echo "$CLEAN_JSON" | jq -e 'type == "array" and (all(.[]; has("provider") and has("version")))' > /dev/null