Migrate sizes harness invocations to generic_cylinders.py

[DLWoodruff]

Summary

• Archive examples/sizes/sizes_ef.py, sizes_ph.py, and sizes_pysp.py under examples/sizes/archive/. The first two have no callers anywhere; the PySP-based EF driver is only referenced from run_all.py and is redundant with generic_cylinders.py --EF.
• examples/run_all.py: replace the sizes_pysp.py EF line with generic_cylinders.py --module-name sizes --EF, and add a parallel generic_cylinders.py PH entry alongside the rst-documented sizes_cylinders.py one so the harness exercises both patterns.
• doc/src/examples.rst: reword the sizes section to point new users at the generic driver; sizes_cylinders.py is retained as the worked cylinders example and sizes_demo.py as the serial variant used by the extensions docs.

Retained in the directory (all still used): sizes.py (model module), sizes_cylinders.py (examples.rst), sizes_demo.py (cited ~8x across drivers/examples/extensions rst), sizes_expression.py (exercised by generic_tester.py for the lp/mps path), special_cylinders.py / special_sizes.py (used by run_all.py developer-only path and tryone.py).

Test plan

• python ../../mpisppy/generic_cylinders.py --module-name sizes --num-scens=3 --EF --EF-solver-name=gurobi_persistent — objective 224275.33
• mpiexec -np 3 python -m mpi4py ../../mpisppy/generic_cylinders.py --module-name sizes --num-scens=10 --max-iterations=5 --default-rho=1 --lagrangian --xhatxbar --linearize-proximal-terms --iter0-mipgap=0.01 --iterk-mipgap=0.001 --solver-name=gurobi_persistent — PH + lagrangian + xhatxbar converges to 1.5% cylinder gap
• ruff check examples/run_all.py
• CI run_all / generic_tester jobs on this PR

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.74%. Comparing base (4bd0393) to head (e8ac5f8).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #660      +/-   ##
==========================================
+ Coverage   70.73%   70.74%   +0.01%     
==========================================
  Files         153      153              
  Lines       19011    19011              
==========================================
+ Hits        13447    13449       +2     
+ Misses       5564     5562       -2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.