Reduce LogStep formatting allocations

[AhmedSalih3d]

Motivation

• The per-iteration LogStep path incurred repeated string formatting allocations which are hot in the time-stepping loop and can impact performance.

Description

• Added a pre-parsed Printf.Format field (FormatSpec) and a reusable IOBuffer (StepBuffer) to SimulationLogger to avoid reallocating format state and temporary strings on every LogStep call.
• Pre-parse the progress format in the constructor with Printf.Format(format_string) and allocate a single IOBuffer() for reuse.
• Replaced the previous cfmt join-based line construction in LogStep with Printf.format writing into the reusable buffer and then logging String(take!(buffer)), while leaving the header formatting intact.
• Change applied to src/SimulationLoggerConfiguration.jl and preserves existing log output semantics.

Testing

• No automated tests were run against this change.
• Commands executed while preparing the patch include ls, cat AGENTS.md, rg to locate call sites, multiple sed/nl inspections of files, apply_patch to apply changes, git status, git add, and git commit, and the commit completed successfully.

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