chore(deps): raise conda-petsc floor to >=3.25 (FMG/rotation API consistency)

[lmoresi]

Why

The conda-petsc environments (default/dev/runtime + mpich/openmpi) pinned petsc/petsc4py >=3.21, resolving to 3.24.x. The custom hierarchical FMG uses a petsc4py 3.25 API — PETSc.KSP.DMActive (custom_mg.py:433) — so test_1015/1016/1017 fail on the conda env with AttributeError, even though they pass on the custom amr build (petsc4py 3.25). The conda dev env was inconsistent with both the code and the custom build.

Change

Raise the conda-petsc floor to >=3.25,<4 (petsc 3.25.3 + petsc4py 3.25.3 numpy-2 builds are on conda-forge). Now petsc ↔ petsc4py agree at 3.25, DMActive is present, and the conda dev env matches the custom amr build.

Validation

Re-solved dev (petsc4py 3.25.3, numpy 2.5.0): the custom-MG / SBR / rotated-free-slip / FMG-lockout suite passes — test_1015/1016/1017/1018/1020, 29 passed. This confirms the custom hierarchical FMG is numpy-2 clean and closes the local-validation gap tracked in #303.

Follow-on for #247's min-PETSc note: the effective floor for full functionality (custom FMG) is 3.25, not 3.21.

Underworld development team with AI support from Claude Code

[Copilot]

Pull request overview

This PR updates the pixi conda-forge PETSc feature definitions to require PETSc/petsc4py 3.25+, aligning the conda environments with the petsc4py API usage in custom_mg.py (notably PETSc.KSP.DMActive), and preventing conda-env test failures caused by resolving to petsc4py 3.24.x.

Changes:

• Raise petsc minimum version in conda-petsc features from >=3.21,<4 to >=3.25,<4.
• Raise petsc4py minimum version in conda-petsc features from >=3.21,<4 to >=3.25,<4.
• Apply the same floor consistently across default, mpich, and openmpi conda-petsc feature variants.

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[lmoresi]

Thanks @copilot-pull-request-reviewer — the summary is accurate. To add the validation context behind it:

• The 3.25 requirement is real, not conservative: custom_mg.py:433 uses PETSc.KSP.DMActive.OPERATOR (a petsc4py 3.25 enum) to call KSPSetDMActive(OPERATOR, False) — absent in 3.24.x, so the conda env raised AttributeError and couldn't run the custom-FMG suite at all.
• conda-forge ships petsc/petsc4py 3.25.3 with numpy-2 builds, so the floor resolves cleanly (verified: pixi lock upgraded petsc 3.24.5→3.25.3, petsc4py 3.24.4→3.25.3).
• Post-bump the re-solved dev env (petsc4py 3.25.3 + numpy 2.5.0) runs the full custom-MG / SBR / rotated-free-slip / FMG-lockout suite green (test_1015/1016/1017/1018/1020 — 29 passed), which also confirms the custom hierarchical FMG is numpy-2 clean.

No source changes — config-only floor bump, so the API contract now matches the code.