chore(repo): ignore .superpowers/

The subagent-driven-development ledger and task briefs live in .superpowers/;
keep them out of the repository by construction.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

Author: NetDevAutomate

.gitignore

@@ -657,3 +657,6 @@ docs/release-process.md
 docs/mcp.md
 docs/audhd-deep-technical-learning-roadmap.md
 docs/audhd-learning-loop-implementation.md
+
+# Superpower plugin
+.superpowers/