chore(repo): move placeholder provider crates to crates/providers/experimental/

README.md

@@ -114,6 +114,7 @@ For more detailed information, please refer to the following documents:
 - **[docs/troubleshooting.md](docs/troubleshooting.md)**: Help with common issues.
 - **[docs/provider-implementation.md](docs/provider-implementation.md)**: Trait-level details for implementing providers.
 - **[docs/adding-providers.md](docs/adding-providers.md)**: Step-by-step checklist for wiring a provider into the multi-provider architecture and test suite.
+- **Experimental providers staging area**: [crates/providers/experimental/README.md](crates/providers/experimental/README.md) records the placeholder crates (OpenAI, Anthropic, Gemini) and their current status.
 - **[docs/platform-support.md](docs/platform-support.md)**: Current OS support matrix and cross-check instructions.
 
 ## Configuration

crates/providers/experimental/README.md

@@ -0,0 +1,13 @@
+# Experimental Providers
+
+This directory collects non-workspace placeholder crates for potential
+third-party providers. The code under the following folders is not yet
+implemented and is kept out of the default Cargo workspace to avoid
+confusion:
+
+- `openai`
+- `anthropic`
+- `gemini`
+
+If you want to explore or contribute to these providers, start by reading
+the `README.md` inside each crate for the current status and ideas.