docs: PRD + playbook REA + laporan modul 1 (composerize)

.gitignore

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+# Build artifacts
+/tia
+/dist/
+*.exe
+
+# Reference repos for REA (analisis saja — jangan pernah di-commit)
+/reference/
+
+# OS / editor
+.DS_Store
+*.swp
+.idea/
+.vscode/
+
+# Local test sandbox
+/tmp/