feat(plugin-sentry): add plugin for sentry (#547)

Co-authored-by: JH.Lee <contact@jins.dev>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 3 people

.changeset/fix-plugin-sentry.md

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+---
+"@stackflow/plugin-sentry": minor
+---
+
+feat(plugin-sentry): add Sentry browser tracing plugin for Stackflow navigation events

.pnp.cjs

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+# plugin-sentry
+
+Stackflow plugin for Sentry browser tracing. Automatically creates navigation spans and breadcrumbs for activity transitions (`push`, `pop`, `replace`) and step transitions (`stepPush`, `stepPop`, `stepReplace`).
+
+## Setup
+
+1. Initialize Sentry with the `stackflowBrowserTracingIntegration`:
+
+```typescript
+import * as Sentry from "@sentry/browser";
+import { stackflowBrowserTracingIntegration } from "@stackflow/plugin-sentry";
+
+Sentry.init({
+  dsn: "https://xxx.ingest.us.sentry.io/xxx",
+  integrations: [
+    stackflowBrowserTracingIntegration(),
+    // ... other integrations
+  ],
+});
+```
+
+2. Add `sentryPlugin()` to your stackflow configuration:
+
+```typescript
+import { stackflow } from "@stackflow/react";
+import { sentryPlugin } from "@stackflow/plugin-sentry";
+
+const { Stack, useFlow } = stackflow({
+  activities: {
+    // ...
+  },
+  plugins: [
+    sentryPlugin(),
+    // ... other plugins
+  ],
+});
+```

.yarn/cache/@sentry-browser-npm-10.46.0-91e2f4dcc5-f447c01f96.zip

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+const { context } = require("esbuild");
+const config = require("@stackflow/esbuild-config");
+const pkg = require("./package.json");
+
+const watch = process.argv.includes("--watch");
+const external = Object.keys({
+  ...pkg.dependencies,
+  ...pkg.peerDependencies,
+});
+
+Promise.all([
+  context({
+    ...config({}),
+    format: "cjs",
+    external,
+  }).then((ctx) =>
+    watch ? ctx.watch() : ctx.rebuild().then(() => ctx.dispose()),
+  ),
+  context({
+    ...config({}),
+    format: "esm",
+    outExtension: {
+      ".js": ".mjs",
+    },
+    external,
+  }).then((ctx) =>
+    watch ? ctx.watch() : ctx.rebuild().then(() => ctx.dispose()),
+  ),
+]).catch(() => process.exit(1));