chore: add contribution workflow and experiment templates

docs/experiments.md

@@ -0,0 +1,18 @@
+# Experiment index
+
+No experiments have been published in this repository yet. This index tracks actual project directories rather than planned features.
+
+When adding a project, include a relative link, a one-sentence purpose, status, and a quick way to run it. Start with [the experiment README template](experiment-template.md).
+
+## Status guide
+
+- **Idea:** a written question or proposal; no working implementation claimed.
+- **Prototype:** something runs, with known limitations.
+- **Usable:** documented setup and checks support its stated purpose.
+- **Archived:** retained for reference; active maintenance is not implied.
+
+## Entry format
+
+`[Project name](../experiments/project-name/README.md) — What it does. Status: prototype. Try it: see its README.`
+
+Replace the example path with a real project before adding an entry.