`stem_and_suffix` does not exist — tests fail with `ImportError`/`AttributeError`

[bitflicker64]

Bug

Four test files reference stem_and_suffix, a function that does not exist anywhere in the codebase. The correct name is stem_and_affix, defined in core/forms/utils.py.

Impact

• tests/test_adoption.py fails at import time with ImportError: cannot import name 'stem_and_suffix' from 'core.forms.utils'
• tests/test_agent.py, tests/test_compression.py, and tests/test_induction.py fail at runtime with AttributeError: module 'core.forms.morphology' has no attribute 'stem_and_suffix'

Root cause

core/forms/utils.py defines stem_and_affix (not stem_and_suffix). All four test files use the wrong name.

Affected lines

File	Line(s)	Error type
tests/test_adoption.py	18, 50, 132, 136	ImportError at import
tests/test_agent.py	32	AttributeError at runtime
tests/test_compression.py	38, 48	AttributeError at runtime
tests/test_induction.py	33, 41	AttributeError at runtime

Fix

Replace every occurrence of stem_and_suffix with stem_and_affix in the four test files. No production code needs to change. The function signature is identical — (form) -> (stem, affixes).