Fix two NameErrors in the e2e-rag reference implementation

[David-Wu1119]

Summary

Two undefined names in the e2e-rag reference implementation, both flagged by ruff --select F821.

1. evaluation.py — has_reranker is never defined. The reranking step tests availability inline, but the verbose-output branch further down uses a name that does not exist:

if not no_rerank and hasattr(
        rag_db, '_reranker_model') and rag_db._reranker_model is not None:
    ...
# ~90 lines later
if not no_rerank and has_reranker:      # NameError

So retrieve_and_evaluate(..., verbose=True) raises NameError: name 'has_reranker' is not defined whenever reranking actually ran. Fixed by binding the availability check once and using it in both places, which also removes the duplicated attribute chain:

has_reranker = (
    getattr(rag_db, '_reranker_model', None) is not None
)
if not no_rerank and has_reranker:

2. reference_SUT_datasetup.py — log is used before it exists. The ImportError handler for BeautifulSoup logs a warning, but log is only created after the try/except:

try:
    from bs4 import BeautifulSoup
    ...
except ImportError:
    HAVE_HTML = False
    log.warning("BeautifulSoup not available - HTML processing disabled")   # NameError

logging.basicConfig(level=logging.INFO)
log = logging.getLogger("DatasetupSUT")

The point of that handler is to degrade gracefully via HAVE_HTML, but on a machine without bs4 the module fails to import at all with NameError: name 'log' is not defined — so the fallback it implements can never be reached. Fixed by moving the logger setup above the import attempt.

Verification

ruff --select F821 e2e-rag/ is clean afterwards, and both files parse. The second one is the more consequential of the two: it is the difference between "HTML processing disabled" and the reference SUT not importing.

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