Raise an error when simplex reaches max iterations

[Rokesh2008]

Fixes #14584\n\nReopens this contribution with the Ruff EM102 fix applied: the exception message is assigned before raising ValueError.\n\nThe prior PR #15243 was closed before the workflow fix could be applied.

[algorithms-keeper]

Closing this pull request as invalid

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[Rokesh2008]

Closing this out on my end — while checking why this was flagged invalid, I found that the same fix (raising ValueError on simplex non-convergence instead of returning {}) was already merged in #14607, which closed the underlying issue (#14584). Since master already has equivalent behavior, I'll leave this PR closed rather than rebase it. Thanks for the review!