chore: Tell Claude how to run e2e tests

CLAUDE.md

@@ -0,0 +1,25 @@
+# Claude guidance for sentry-electron
+
+## Running the e2e tests
+
+The end-to-end tests in [`test/e2e`](./test/e2e) launch real Electron apps. A few things are required to run them
+successfully, especially from the Claude Code shell:
+
+- **`unset ELECTRON_RUN_AS_NODE` first.** The Claude Code shell exports `ELECTRON_RUN_AS_NODE=1`, which makes every
+  Electron binary run as plain Node. When that happens `require('electron').app` is `undefined` and every test crashes
+  at SDK load (`normalize.js` calling `app.getAppPath()`) or times out. This is not a broken harness — it only affects
+  shells where that variable is set.
+- **Set `ELECTRON_VERSION`.** The runner throws `ELECTRON_VERSION is not set` otherwise. Use a version whose binary is
+  already cached (e.g. `25.9.8`).
+- **Use `yarn e2e`, not a bare `vitest` invocation.** `yarn e2e` runs the `pree2e` step (`set-version`, cache cleanup)
+  that the tests depend on.
+- **`-t` is a regex**, so escape parentheses in test names, e.g. `-t 'Browser Tracing \(Span streaming\)'`.
+- **`DEBUG=true`** prints every received envelope as `[Test Runner] Received event ...`, which is the easiest way to
+  build/verify assertions.
+
+Example — run all span-streaming tests against Electron 25.9.8:
+
+```shell
+unset ELECTRON_RUN_AS_NODE
+DEBUG=true ELECTRON_VERSION=25.9.8 yarn e2e -t 'Span streaming'
+```