ENH: Rename exps_comm_* commission cells to commissions_*

[fumitoh]

Summary

• Continues the 3f738b3 cell-naming standardization in TradLife_A.BaseProj by bringing the commission components under the existing commissions(t) umbrella, mirroring the claims_* / claims_*_pp pattern.
• Renames four cells: exps_comm_init → commissions_init, exps_comm_ren → commissions_ren, exps_comm_init_pp → commissions_init_pp, exps_comm_ren_pp → commissions_ren_pp. Updates call sites in commissions / expenses and the autosummary/autofunction entries in BaseProj.rst.
• Updates the Exps docstring example to exps_maint (no exps_comm_* cell remains as a representative).

Notes for reviewers

• No test files referenced the renamed cells, so no test changes were required.
• data.pickle and the _data/ directory were intentionally untouched — modelx reads cell definitions from __init__.py, and the prior standardization commit followed the same approach.
• The output cell list inside tradlife_a-space-overview.ipynb is left to regenerate naturally on the next notebook execution.

Test plan

• pytest lifelib/tests/libraries/test_tradlife_a.py — 3/3 pass
• Smoke import via modelx: all four new cell names resolve, all four old names absent
• Projection[1] exercise: commissions_init(0) = 588.47, commissions_ren(1) = 135.31, commissions_init_pp(0) = 588.47, commissions_ren_pp(1) = 147.12, with commissions(0) = commissions_init(0) as expected

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