feat(server-utils): Add instrumentation for pi-durable - #24993

Cloudflare now hosts pi-durable in Durable Objects through the Agents
SDK `PiHarness`
([changelog](https://developers.cloudflare.com/changelog/post/2026-10-02-pi-harness/)).
This app runs pi-durable that way, with `@sentry/cloudflare/vite` as the
only Sentry setup. It checks that a prompt becomes an `invoke_agent`
trace with `chat`, `execute_tool` and provider `http.client` spans, that
a throwing tool is reported on its span, and that a run resumes in a new
trace after the Durable Object resets during a tool call. The reset uses
`ctx.abort()`, which drops the object like an eviction; the next request
starts it again, and `PiHarness` resumes pi from its SQLite state.

Like `node-pi-durable` and `cloudflare-think`, it calls a real model
through OpenRouter, so it is optional. The changelog example uses
Workers AI (`createAI({ binding: env.AI })`), but the AI binding needs a
Cloudflare account even in local dev, so that path has a unit test in
#24993 instead.

This app found a bug that #24993 now fixes: `@sentry/cloudflare`
initializes the SDK inside each request, so the client is on the scope
of that request only. The task phases ran on a copy of the default
scope, had no client, and dropped every pi-durable span and error.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

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## DESCRIBE YOUR PR

Adds a dedicated `javascript.pi-durable` platform guide for the Pi
Durable integration added in getsentry/sentry-javascript#24993 (see also
the [Pi Durable announcement](https://earendil.com/posts/pi-durable/)).
It follows the same structure as the Flue, Eve, and Mastra guides.

- `docs/platforms/javascript/guides/pi-durable/index.mdx`: Node.js setup
(preload `instrument.mjs` with `--import`, or use the bundler plugin)
- `docs/platforms/javascript/guides/pi-durable/cloudflare.mdx`:
Cloudflare setup (`sentryCloudflareVitePlugin()` +
`instrument.server.ts`, with an Agents SDK `PiHarness` example)
- `includes/pi-durable/`: shared sections covering experimental status,
captured telemetry (`gen_ai.invoke_agent` / `gen_ai.chat` /
`gen_ai.execute_tool`), conversation IDs across restarts, crash
recovery, captured errors, which provider integrations get skipped,
current gaps, verification, and next steps
- Adds `javascript.pi-durable` to common-page platform lists wherever
Mastra appears (install-method pages stay visible, since a Pi Durable
app controls its own startup)
- Adds a Pi icon (`src/icons/pi-durable.svg`), plus entries on the Agent
Tracing index and the Agents getting-started page

Bun and Deno are left out for now because their setup couldn't be
verified. Only Node and Cloudflare are documented.

## IS YOUR CHANGE URGENT?

- [ ] Urgent deadline (GA date, etc.): YYYY-MM-DD
- [ ] Other deadline: YYYY-MM-DD
- [x] No deadline: Not urgent, can wait up to 1 week+

## SLA

- Teamwork makes the dream work, so please add a reviewer to your PRs.
- Please give the docs team up to 1 week to review your PR unless you've
supplied a deadline.

## PRE-MERGE CHECKLIST

- [ ] Checked Vercel preview for correctness, including links
- [ ] PR was reviewed and approved by any necessary SMEs (subject matter
experts)
- [ ] PR was reviewed and approved by a member of the [Sentry docs
team](https://github.com/orgs/getsentry/teams/docs)

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via **Andrei Borza**.
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Co-authored-by: sentry-junior[bot] <264270552+sentry-junior[bot]@users.noreply.github.com>
Co-authored-by: Andrei Borza <andrei.borza@sentry.io>