fix(telemetry): correct runtime context for Bun binary (#231)

## Summary

- Fix incorrect `runtime` tag/context showing `node` instead of `bun`
for native Bun binary
- Override `client.getOptions().runtime` after `Sentry.init()` to work
around `@sentry/bun` v10 bug where `NodeClient` always overrides the
runtime option
- Keep `cli.runtime` tag for backward compatibility with existing
dashboards

## Problem

`@sentry/bun` v10 delegates to `@sentry/node`'s `NodeClient`, which
always overrides `runtime` to `{ name: 'node', version: process.version
}`. Under Bun, `process.version` returns the Node.js compat version
(e.g. `v24.3.0`), causing `event.contexts.runtime` and the
server-promoted `runtime` tag to incorrectly show `node`.

## Fix

Override `client.getOptions().runtime` after `Sentry.init()` with the
correct Bun runtime info. `Sentry.setContext()` doesn't work here
because `ServerRuntimeClient._prepareEvent()` runs before scope context
merging and its result takes precedence.

Upstream issue:
getsentry/sentry-javascript#19269

Author: BYK

src/lib/telemetry.ts

@@ -162,10 +162,27 @@ export function initSentry(enabled: boolean): Sentry.BunClient | undefined {
   });
 
   if (client?.getOptions().enabled) {
-    // Tag whether running as bun binary or node (npm package)
-    // This is CLI-specific context not provided by the Context integration
-    const runtime =
-      typeof process.versions.bun !== "undefined" ? "bun" : "node";
+    const isBun = typeof process.versions.bun !== "undefined";
+    const runtime = isBun ? "bun" : "node";
+
+    // Fix runtime context: @sentry/bun v10 delegates to @sentry/node's NodeClient,
+    // which always overrides runtime to { name: 'node', version: process.version }.
+    // Under Bun, process.version returns the Node.js compat version (e.g. v24.3.0),
+    // not the Bun version. Override it so event.contexts.runtime is correct and
+    // Sentry's server-side tag promotion creates an accurate 'runtime' tag.
+    // TODO: Remove once fixed upstream: https://github.com/getsentry/sentry-javascript/issues/19269
+    if (isBun) {
+      // biome-ignore lint/suspicious/noExplicitAny: accessing internal SDK option not exposed in NodeClientOptions
+      const options = client.getOptions() as any;
+      options.runtime = {
+        name: "bun",
+        version: process.versions.bun as string,
+      };
+    }
+
+    // Tag whether running as bun binary or node (npm package).
+    // Kept alongside the SDK's promoted 'runtime' tag for explicit signaling
+    // and backward compatibility with existing dashboards/alerts.
     Sentry.setTag("cli.runtime", runtime);
 
     // Tag whether targeting self-hosted Sentry (not SaaS)