chore: add consistent mise.toml, justfile, and tooling config

justfile

@@ -0,0 +1,22 @@
+set shell := ["bash", "-c"]
+
+default: check
+
+[private]
+_ensure_tools:
+    @mise trust --yes . 2>/dev/null; mise install --quiet
+
+# Run all checks (fmt, lint)
+check: fmt-check lint
+
+# Format code
+fmt: _ensure_tools
+    @uv run ruff format .
+
+# Check formatting without changing files
+fmt-check: _ensure_tools
+    @uv run ruff format --check .
+
+# Lint
+lint: _ensure_tools
+    @uv run ruff check .