fix: remove duplicate use std::fmt::Write;

[Tcode-Motion]

This removes a duplicate import of std::fmt::Write in cli/src/diagnostics.rs and cli/src/profiler.rs that was causing the cargo build --workspace and subsequent cargo test --workspace checks to fail on CI workflows due to duplicate definition errors. The project compiles successfully and all tests pass with this change.

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PR created automatically by Jules for task 11685079548447595931 started by @Tcode-Motion

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