chore: add reports/ to .gitignore and remove tracked reports

- Add reports/ directory to .gitignore (ephemeral artifacts should not be versioned)
- Remove tracked reports files from git (they are generated artifacts)
- Aligns with directory structure documentation where reports/ is gitignored

Author: Dominikus Nold

.gitignore

@@ -108,6 +108,9 @@ specs/
 # Ignore .specfact artifacts
 .specfact/
 
+# Ignore reports directory (ephemeral artifacts)
+reports/
+
 # Ignore mcp.json
 .github/mcp.json
 .cursor/mcp.json