chore: Root-.gitignore für node_modules-Cache und SDD-Arbeitsnotizen

Refs #41

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

.gitignore

@@ -0,0 +1,9 @@
+# Root-level artefacts only; each project has its own .gitignore.
+
+# Tool caches created when tests or scripts run from the repo root.
+/node_modules/
+
+# Working notes of the SDD orchestration (ledgers, briefs, review reports)
+# and design mockups/screenshots (~90 MB). Decisions that matter are in
+# ARCHITECTURE.md, the specs/plans under docs/ and the Gitea issues.
+/.superpowers/