docs: scaffold polisher-control foundation

.gitignore

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+# Python
+__pycache__/
+*.py[cod]
+.pytest_cache/
+.ruff_cache/
+.mypy_cache/
+.venv/
+venv/
+*.egg-info/
+
+# PlatformIO / embedded
+.pio/
+.vscode/.browse.c_cpp.db*
+.vscode/c_cpp_properties.json
+
+# Runtime data: never commit real run data
+/data/
+data/runs/
+data/manual/
+*.parquet
+*.npz
+
+# Local config/secrets
+.env
+*.local.*
+secrets.*