fix(runtime): owner-aware registry entry removal

[sam-goodwin]

A replacement instance of the same script re-registers under the same registry key. When the superseded instance's scope closes afterwards (a make-before-break handoff), its unregister finalizer deleted {scriptName}.json — unregistering the live replacement and breaking cross-script resolution.

Removal (both the scope finalizer and the exit hook) is now owner-aware — it only deletes the file while it still holds that write's content:

Effect.addFinalizer(() =>
  fs.readFileString(entryPath).pipe(
    Effect.flatMap((current) =>
      current === serialized ? fs.remove(entryPath) : Effect.void,
    ),
    Effect.ignore,
    Effect.andThen(Effect.sync(() => unregister())),
  ),
);

This unblocks reordering alchemy's local dev serve path back to make-before-break (start the replacement workerd before tearing down the previous instance), which alchemy-run/alchemy#812 had inverted precisely because unregister could delete the replacement registration. See alchemy-run/alchemy#859.

[alchemy-version-bot]

Install the packages built from this commit:

@distilled.cloud/cloudflare-rolldown-plugin

bun add https://pkg.distilled.cloud/cloudflare-rolldown-plugin/6c2eebb

@distilled.cloud/cloudflare-runtime

bun add https://pkg.distilled.cloud/cloudflare-runtime/6c2eebb

@distilled.cloud/cloudflare-vite-plugin

bun add https://pkg.distilled.cloud/cloudflare-vite-plugin/6c2eebb