[Hotfix Main]: [Snappy] Proximity spacing additional validator

[github-actions]

Hotfix of PR #1949 (#1949) to the main branch.
Hey @piotrkluba, please review this hotfix PR created from your original PR.

⚠️ Note: This PR had conflicts with the base branch and was resolved automatically. Please review the changes carefully.

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Note

Medium Risk
Tightens meshing parameter validation by turning a previous warning/autocorrect into hard errors, which can break existing configs that relied on implicit clamping.

Overview
Strengthens snappy surface meshing refinement validation for proximity_spacing.

SnappyEntityRefinement now raises a validation error (instead of logging and clamping) when proximity_spacing > min_spacing. SurfaceMeshingParams adds an additional check for BodyRefinement that omits min_spacing: it rejects proximity_spacing values that exceed defaults.min_spacing.

Adds focused tests covering the new error and non-error cases.

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