fix: pin host root_base to a C++23 ROOT build

[olantwin]

Problem

When shipdatamodel is built as a source dependency (e.g. in aegir's dev environment via shipdatamodel = { path = "../data-model" }), a fresh resolve fails:

root >=6.40 cannot be installed because there are no viable options:
  root 6.40.0 | ... | 6.40.2 would require
    └─ root_base ==6.40.0 cxx20_h3697410_0, for which no candidates were found.

pixi-build-cmake exact-pins the root_base build it resolves in the host environment into shipdatamodel's run-export, and its host solve does not honour the root_cxx_standard == "==23" host dependency. So root_base = "*" can resolve to a cxx20 build, and the resulting cxx20 run-export conflicts with the C++23 stack (root_cxx_standard == "==23") in the consuming environment. (The build string is present in conda-forge's repodata — the "no candidates" is really "no cxx20 candidate compatible with root_cxx_standard==23".)

The released shipdatamodel (conda-forge-style recipe) does not hit this because it gets a range run-export (root_base >=6.40.2,<6.40.3) via root_base's run_exports and the root_cxx_standard variant — machinery the pixi-build path lacks.

Fix

Constrain the host root_base to a cxx23_* build so the emitted run-export stays cxx23-compatible.

root_base = { version = "*", build = "cxx23_*" }

Verified locally (pixi 0.68.1): with this change the fresh dev-environment resolve gets past the root_base conflict and proceeds to build shipdatamodel.

Can be dropped once pixi-build honours root_cxx_standard in the host solve, or uses root_base's run_exports range instead of an exact-build pin (upstream issue to be filed).

Notes

This is the first of a chain of latent, lock-masked conflicts exposed by aegir's fresh dev-source resolve; a separate geomodel-core skew between shipgeometry and shipgeometryservice is tracked independently.

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📥 Commits

Reviewing files that changed from the base of the PR and between 4eb1498 and 714e638.

📒 Files selected for processing (1)

• pixi.toml

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/host-root-base-cxx23

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