fix(embed): pass --no-save to interactive TTY install

The non-TTY auto-install path already passes `--no-save`. The TTY path did
not, which was fine when `cwd` defaulted to `process.cwd()` because that
already polluted the user's working dir (a separate, original bug).

Now that `cwd` is pinned to codegraph's host directory, omitting
`--no-save` would silently add `@huggingface/transformers` to the
`package.json` sitting next to codegraph's `node_modules` (the user's
project root when codegraph is a local dep, or the npm global prefix when
global-installed). Match the non-TTY path so installs stay ephemeral
regardless of code path.

Updates the corresponding assertion in tests/unit/prompt-install.test.ts.

Author: carlos-alm

src/domain/search/models.ts

@@ -160,7 +160,7 @@ export function promptInstall(packageName: string): Promise<boolean> {
         rl.close();
         if (answer.trim().toLowerCase() !== 'y') return resolve(false);
         try {
-          execFileSync(NPM_BIN, ['install', packageName], {
+          execFileSync(NPM_BIN, ['install', '--no-save', packageName], {
             stdio: 'inherit',
             timeout: 300_000,
             cwd: installCwd,

tests/unit/prompt-install.test.ts

@@ -151,7 +151,7 @@ describe('loadTransformers install prompt', () => {
     });
     expect(execMock).toHaveBeenCalledWith(
       expectedNpmBin,
-      ['install', '@huggingface/transformers'],
+      ['install', '--no-save', '@huggingface/transformers'],
       expect.objectContaining({ stdio: 'inherit', timeout: 300_000 }),
     );
   });