Convert the scanner's plist parser and Node-style file shim to TypeScript and add small unit tests so common parser and file-reader failures are caught before we need to lean on Playwright or the higher-level scanner test.
Constraint: Must preserve current scanner behavior while tightening the lowest-level helper surface
Rejected: Jump straight to Mach-O parser conversion | harder to isolate regressions without first proving the smaller helper-test pattern
Confidence: high
Scope-risk: narrow
Reversibility: clean
Directive: Add small module-level regression tests for repeatable scanner breakage before expanding browser coverage
Tested: pnpm run typecheck; pnpm exec vitest run test/scanner/plist.test.ts test/scanner/file-api.test.ts test/scanner/client.test.ts; pnpm run test; pnpm run test:browser
Not-tested: Production deploy behavior prior to push
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)
