refactor(scanner): type the worker path and align app-test results

Move the worker scanner surface into TypeScript, add a direct worker regression, and make the version=2 app-test path populate the same visible result data and final status as the legacy scanner. This keeps the refactor bounded while making the worker route safe to exercise.

Constraint: Must preserve the existing Apple Silicon app-test behavior while changing the worker internals
Rejected: Flip production to the worker path immediately | still needs the normal deploy path and broader production soak
Confidence: medium
Scope-risk: moderate
Reversibility: clean
Directive: Keep the version=2 adapter using the shared finishFileScan path until the legacy scanner can be removed entirely
Tested: pnpm run typecheck; pnpm exec vitest run test/scanner/client.test.ts; pnpm run test:browser (original workspace); netlify build --context deploy-preview (original workspace)
Not-tested: Browser suite from the clean clone environment (local Astro dev server startup timed out there)

test/playwright/support/app-archive-fixture.ts

@@ -58,11 +58,10 @@ export async function createNativeAppArchive ( appName = 'Playwright Native App'
 
         const archiveBuffer = await readFile( archivePath )
 
+        const archiveArrayBuffer = new Uint8Array( archiveBuffer ).slice().buffer
+
         return {
-            arrayBuffer: archiveBuffer.buffer.slice(
-                archiveBuffer.byteOffset,
-                archiveBuffer.byteOffset + archiveBuffer.byteLength
-            ),
+            arrayBuffer: archiveArrayBuffer,
             buffer: archiveBuffer,
             mimeType: 'application/zip',
             name: `${ appName }.app.zip`,