Restore KVzip forward after context errors 🤖🤖🤖

[fallintoplace]

Summary

• Restore model.model.forward from an inner finally around the KVzip context yield.
• Preserve the normal path where the original forward is restored before KVzip's post-yield compression/scoring phase.
• Add regression coverage for both exceptional context exits and normal compression setup.

Root cause

KVzipPress.__call__ monkey-patches model.model.forward before yielding to the caller, but the original method was restored only after a normal return from the with block. If the caller raised inside the context, the outer cleanup removed hooks and reset internal state without restoring forward, leaving the model patched after exit.

Validation

• uv run pytest tests/presses/test_kvzip_press.py
• uv run isort kvpress/presses/kvzip_press.py tests/presses/test_kvzip_press.py
• uv run black kvpress/presses/kvzip_press.py tests/presses/test_kvzip_press.py
• uv run flake8 kvpress/presses/kvzip_press.py tests/presses/test_kvzip_press.py
• uv run mypy kvpress/presses/kvzip_press.py --check-untyped-defs
• make style

[copy-pr-bot]

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