Dependency cleanup phase 2: CI runners consume the [test] extra

[DLWoodruff]

Second of three PRs implementing doc/designs/dependency_cleanup_design.md (first: #811, merged; third will add attempt_import guards for the four opt-in modules).

Per §4 of the design doc, every CI job's hand-rolled feature-package pip list is replaced by pip install -e ".[test]" at the existing editable-install step, so adding a test dependency becomes a one-line pyproject.toml change instead of ~12 YAML edits. Touches test_pr_and_main.yml, pyotracker.yml, and test_uc_weekly.yml; net −2 lines with more of the remaining lines being comments.

What stays explicit, per job

• Solvers (cplex, xpress, gurobipy, highspy) — deliberately in no extra (licensing).
• pyomo + pybind11 in the five jobs whose pyomo build-extensions step runs before the editable install (regression, the four run_all jobs, generic_tester).
• Git installs: parapint/pyutilib/git-pyomo in schur-complement; the git egret in test_uc_weekly.yml (installed before [test], so it satisfies the extra's gridx-egret requirement and is not replaced).
• conda lines (mpi4py pandas setuptools etc.) — conda jobs get mpi4py from conda, so [mpi] is unnecessary in CI.
• pyyaml in test-headers, and test-pysp's conda pytest pyyaml networkx.

Deliberate changes beyond pure consolidation

• uc-relaxed now uses gridx-egret from the [test] extra instead of a git egret install — standardizing on the released egret in the PR workflow; the git egret lives only in the weekly UC workflow.
• sphinx dropped from non-doc jobs; the two jobs that run make doctest (regression, pyotracker) use ".[test,doc]".
• sympy and Pympler installs dropped entirely — neither is imported anywhere in mpisppy/ or examples/ (cargo-cult carryover).
• The no-solver unit-tests job now installs the feature packages (scipy, dill, etc. arrive via [test]), so optional-dependency test paths that were silently skipped there now run.

The ruff job's pinned astral-sh/ruff-action@v3 (0.15.21, from #812) is untouched.

Verification

The full matrix running on this PR is the verification, per the design doc ("it already runs on PRs"). The two scheduled workflows (pyotracker, test_uc_weekly) don't run on PRs; their edits follow the identical pattern, and test_uc_weekly supports workflow_dispatch for a manual check after merge.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.59%. Comparing base (89c7693) to head (b8c25e1).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #821   +/-   ##
=======================================
  Coverage   76.59%   76.59%           
=======================================
  Files         175      175           
  Lines       23239    23239           
=======================================
+ Hits        17799    17801    +2     
+ Misses       5440     5438    -2     

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