test(cloudflare): pin OTLP event-telemetry contracts; fix teardown-hook cleanup leaks

[sam-goodwin]

Resolves the investigation behind #1331 / #1332: the runtime bridges need no change — the existing waitUntil-deferred background export delivers every batch, verified empirically on local and deployed workerd for Worker fetch, DO fetch, and DO RPC events. The loss in #1331's repro was the test harness tearing workerd down before background work ran (#1341 fixes the Vitest adapter). This PR pins the telemetry contracts as tests, and fixes the same teardown-leak class in the two other test adapters.

Telemetry contract tests (no bridge changes)

environment	Worker fetch	DO fetch	DO RPC
local workerd (dev sidecar, alive)	✓	✓	✓
deployed workerd	✓	✓	✓

• Delivery — every event's OTLP batch reaches the collector while the runtime is alive. Locally via a 500ms-delayed 127.0.0.1 collector counting only fully-written responses; live via the DO-backed collector on the test zone (Telemetry.test.ts now also deploys the Worker→DO fixture and asserts the DO fetch and DO RPC event spans arrive from deployed workerd — state.waitUntil is a no-op in DOs, so this is the path Cloudflare event-scoped OTLP batches can be dropped during background scope close #1331 believed was broken).
• Latency — an event's response never waits on its own telemetry export:

const completedAtResponse = collector.completedRequests.value;
expect(completedAtResponse).toBeLessThanOrEqual(1); // own batch still in flight

A foreground-flush design fails the latency bound; a lossy design fails the delivery poll.

Teardown-hook leak fixes (companion to #1341)

A failing teardown hook silently dropped later cleanup — leaking the shared scope and local provider sidecar for the rest of the test process. Each adapter had it with a different trigger; #1341 covers Vitest, this covers the other two:

• alchemy-test runner: runAfterAll short-circuited on the first failing hook. Every afterAll now runs; failures aggregate. (beforeAll keeps short-circuit semantics — a failed setup invalidates what follows.)
• Test/Bun: bun:test stops the afterAll chain once a hook throws (probed empirically; registration order and afterAll-after-failed-beforeAll are fine), skipping the microtask-registered fallback. User teardowns are now guarded:

const guardTeardown = (eff) => () =>
  runEff(eff).catch(async (error) => {
    await Effect.runPromise(closeAll); // idempotent
    throw error;                       // still fails the suite
  });

Both regression tests are two-sided and red against the previous code: the runner test asserts a second teardown's sentinel after a failing first; the Bun test spawns real bun test on a fixture using the public adapter and asserts a shared-scope finalizer sentinel after the throwing user teardown.

Builds on @dmmulroy's investigation and repro topology from #1331/#1332.

[sam-goodwin]

cc @dmmulroy

[alchemy-version-bot]

Install the packages built from this commit:

Alchemy

alchemy

bun add https://pkg.ing/alchemy/987fd5c

@alchemy.run/better-auth

bun add https://pkg.ing/@alchemy.run/better-auth/987fd5c

@alchemy.run/cloudflare-runtime

bun add https://pkg.ing/@alchemy.run/cloudflare-runtime/987fd5c

@alchemy.run/frontend-frameworks

bun add https://pkg.ing/@alchemy.run/frontend-frameworks/987fd5c

@alchemy.run/node-utils

bun add https://pkg.ing/@alchemy.run/node-utils/987fd5c

@alchemy.run/pr-package

bun add https://pkg.ing/@alchemy.run/pr-package/987fd5c

@alchemy.run/floci

bun add https://pkg.ing/@alchemy.run/floci/987fd5c

Distilled

@distilled.cloud/core

bun add https://pkg.ing/@distilled.cloud/core/dd2a322

@distilled.cloud/aws

bun add https://pkg.ing/@distilled.cloud/aws/dd2a322

@distilled.cloud/axiom

bun add https://pkg.ing/@distilled.cloud/axiom/dd2a322

@distilled.cloud/cloudflare

bun add https://pkg.ing/@distilled.cloud/cloudflare/dd2a322

@distilled.cloud/hetzner

bun add https://pkg.ing/@distilled.cloud/hetzner/dd2a322

@distilled.cloud/neon

bun add https://pkg.ing/@distilled.cloud/neon/dd2a322

@distilled.cloud/planetscale

bun add https://pkg.ing/@distilled.cloud/planetscale/dd2a322