[codex] Fix vulnerable example dependencies

[koo-ec]

Summary

• Updates the Pix2Pix example dependency constraints and lockfile to patched versions for the GitHub security alert set.
• Updates the Tabular example lockfile to use Pygments 2.20.0.
• Removes img2img-turbo from the default Pix2Pix dependency set because img2img-turbo 0.0.1 pins transformers < 4.58, which conflicts with the security-patched transformers 5.x target. The I2I-Turbo path now lazy-loads it and raises a clear runtime error if that optional path is used without a compatible install.
• Keeps the Pix2Pix notebook install cell aligned with the patched dependency set.
• Fixes the existing CI lint blockers in examples/Tabular_Example/smile_tabular.py, xwhy/smile_graph.py, and xwhy/smile_text.py so the PR can pass the strict flake8 syntax/undefined-name gate.

Validation

• uv --cache-dir C:\Users\Koo\Documents\Codex\2026-05-26\help-me-to-fix-the-following\.uv-cache lock --check --no-managed-python --python python in examples/Pix2Pix_Instruct
• uv --cache-dir C:\Users\Koo\Documents\Codex\2026-05-26\help-me-to-fix-the-following\.uv-cache lock --check --no-managed-python --python python in examples/Tabular_Example
• python -m py_compile examples\Pix2Pix_Instruct\smile_for_instruction_based_image_editing.py
• notebook JSON parse check for examples/Pix2Pix_Instruct/SMILE_for_Instruction_based_Image_Editing.ipynb
• python -m compileall -q xwhy examples
• uv --cache-dir C:\Users\Koo\Documents\Codex\2026-05-26\help-me-to-fix-the-following\.uv-cache --no-managed-python tool run --python python flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
• git diff --check