fix: dispose Cloudflare platform proxy when Vite servers close

[svelte-triage-bot]

Closes #16919

The Cloudflare adapter no longer creates its platform proxy during builds, but the proxy created for Vite dev and preview servers was still retained after those servers closed.

This change retains the proxy in the adapter plugin and disposes it:

• through Vite's awaited closeBundle lifecycle for dev servers
• through the preview server's close() lifecycle
• idempotently when multiple close hooks run
• while clearing the global proxy so a later server can create a fresh instance

Added focused tests covering dev and preview teardown and a patch changeset.

Verification:

• pnpm -F @sveltejs/adapter-cloudflare test:unit
• pnpm -F @sveltejs/adapter-cloudflare check
• pnpm -F @sveltejs/kit test:unit
• pnpm check
• pnpm lint
• Cloudflare workers fixture build, with zero workerd processes before and after

[pkg-svelte-dev]

Install the latest version of @sveltejs/kit from 2c82e22:

pnpm add https://pkg.svelte.dev/@sveltejs/kit/c/2c82e227c6a8c7d40a3546f224e639ea7d940562

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/kit/pr/16976

Note

This PR is from a fork. A maintainer must approve approve each commit before it can be built and installed.

[changeset-bot]

🦋 Changeset detected

Latest commit: 2c82e22

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@sveltejs/adapter-cloudflare	Patch

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