feat: add README files for various directories to document structure and usage

scripts/README.md

@@ -0,0 +1,13 @@
+# Build and Quality Scripts
+
+This directory contains the Python implementation of setup, dependency locking,
+build manifests, flow execution, simulation checks, regression orchestration,
+quality checks, metrics, packaging, and cleanup.
+
+Scripts are part of the build contract. Prefer existing helpers over ad-hoc
+shell behavior, preserve structured JSON results, and keep setup/download
+behavior controlled by `config/dependencies.lock.json`.
+
+Update or add tests in [`../tests`](../tests) for script behavior. Run
+`ruff check .` and `python3 -m pytest -q`; build-flow changes also require the
+relevant dry-run or regression profile from [`AGENTS.md`](../AGENTS.md).