refactor(rust): move crate under crates and add release guide

Author: swalker326

packages/rust/tanstack-ai/Cargo.lock crates/tanstack-ai/Cargo.lockpackages/rust/tanstack-ai/Cargo.lock renamed to crates/tanstack-ai/Cargo.lock

@@ -0,0 +1,49 @@
+# tanstack-ai release process
+
+This document describes how to publish the Rust crate to crates.io.
+
+## Prerequisites
+
+- crates.io owner access for `tanstack-ai`
+- `cargo` authenticated (`cargo login <TOKEN>`), or `CARGO_REGISTRY_TOKEN` set
+- all intended changes merged to `main`
+
+## 1) Bump version
+
+Update `version` in `crates/tanstack-ai/Cargo.toml`.
+
+## 2) Validate locally
+
+From repo root:
+
+```bash
+cargo test --manifest-path crates/tanstack-ai/Cargo.toml
+cargo package --manifest-path crates/tanstack-ai/Cargo.toml
+```
+
+`cargo package` verifies the crate can be built from the published archive.
+
+## 3) Publish
+
+From repo root:
+
+```bash
+cargo publish --manifest-path crates/tanstack-ai/Cargo.toml
+```
+
+If needed, publish with an explicit token:
+
+```bash
+CARGO_REGISTRY_TOKEN=<token> cargo publish --manifest-path crates/tanstack-ai/Cargo.toml
+```
+
+## 4) Tag and notes
+
+Create a git tag after publish, for example:
+
+```bash
+git tag rust/tanstack-ai-v0.1.0
+git push origin rust/tanstack-ai-v0.1.0
+```
+
+Then document highlights in the GitHub release notes.