fix(eagle): Add robust error handling for missing feature files in patient encoding

[drgmo]

--fix:
try-except-block prevents prevent the process from crashing when feature files listed in the slide table are missing or inaccessible.

--background:

encode_slides_: Iterates over os.listdir(feat_dir). This naturally filters out missing files because it only attempts to process files that the OS reports as present.
encode_patients_: Iterates over a pandas DataFrame (patient_groups). If the csv contains a reference to a slide filename that does not exist on disk, the direct file access causes a FileNotFoundError or OSError, crashing the entire pipeline