tests: pin ink engine in _make_tui_argv npm-bootstrap tests (post-merge semantic fix)

Main's rewritten test_tui_npm_install.py tests call _make_tui_argv expecting
the Ink/npm flow unconditionally; with the dual-engine dispatch merged in,
_resolve_tui_engine() auto-selects opentui whenever ui-opentui/dist is built
in the repo, routing the call away from the path under test (first subprocess
became 'node --version' instead of 'npm run build'). Pin the engine to ink
via an autouse fixture, mirroring the existing pinning precedent in
test_tui_resume_flow.py.

plugins/memory/byterover/__init__.py

@@ -94,6 +94,7 @@ def _run_brv(args: List[str], timeout: int = _QUERY_TIMEOUT,
         result = subprocess.run(
             cmd, capture_output=True, text=True,
             timeout=timeout, cwd=effective_cwd, env=env,
+            stdin=subprocess.DEVNULL,
         )
         stdout = result.stdout.strip()
         stderr = result.stderr.strip()