`ember-tsc --watch` fails to resolve extensionless GTS imports

The language server and single-shot `ember-tsc` seem to both work fine, but specifically with the `--watch` flag, things fall apart. I first noticed it in the context of absolute imports and started to put together [a reproduction of that](https://github.com/typed-ember/glint/compare/main...dfreeman:glint:watch-issue), but then realised the existing `ts-template-imports-app` in this repo already exhibits the issue. To reproduce on `main`: ``` cd test-packages/ts-template-imports-app pnpm test:typecheck # ✅ pnpm test:typecheck --watch # 💥 ``` ``` [15:35:19] Starting compilation in watch mode... src/index.gts:1:22 - error TS2307: Cannot find module './Greeting' or its corresponding type declarations. 1 import Greeting from './Greeting'; ~~~~~~~~~~~~ [15:35:20] Found 1 error. Watching for file changes. ```