BUG: flex op with ExtensionArray and fill_value

[jbrockmendel]

Pandas version checks

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Reproducible Example

import pandas as pd
left = pd.Series([pd.Timestamp(2025, 8, 20)] * 2)

right = left._values

left.sub(right, fill_value=left[0])  # <- raises

Issue Description

In Series._flex_method we have a check for elif isinstance(other, (np.ndarray, list, tuple)): that should include ExtensionArray

Expected Behavior

N/A

Installed Versions

Replace this line with the output of pd.show_versions()

[praateekmahajan]

take