Add test runner skill documentation for Claude

.claude/skills/test-runner.md

@@ -0,0 +1,31 @@
+---
+name: running-tests
+description: Runs the project test suite using cargo-nextest, including unit and integration tests. Use when the user asks to run tests, verify changes, or validate before committing.
+---
+
+# Running Tests
+
+## Prerequisites
+
+If the environment is not set up, run `cargo xtask claude setup`.
+
+## Full test suite
+
+```sh
+cargo nextest run --locked --all-targets --all-features --no-fail-fast
+```
+
+Nextest automatically builds WASM test binaries via `.config/nextest.toml` setup scripts before running tests.
+
+## Specific test or crate
+
+```sh
+cargo nextest run --locked --all-features test_name
+cargo nextest run --locked --all-features -p crate-name
+```
+
+## Key details
+
+- Integration tests use `#[sqlx::test]` and require `DATABASE_URL` to be set (the session-start hook writes `.env`).
+- The nextest setup script runs `cargo component build --profile wasm -p durable-test-workflows` to build WASM binaries loaded by tests at runtime.
+- CI uses the `dev-ci` cargo profile. Add `--cargo-profile dev-ci` for the same behavior locally.