🧹 [code health improvement] Remove dead code attribute in lexer

[Tcode-Motion]

🎯 What: Removed the #[allow(dead_code)] attribute from the LogosToken enum in compiler/lexer/src/lib.rs.
💡 Why: This improves maintainability by allowing the Rust compiler to legitimately check for and highlight unused enum variants, increasing code safety and preventing the accumulation of truly dead code over time.
✅ Verification: Verified by using head to check the file contents, running cargo check -p techscript_lexer, cargo build -p techscript_lexer --release, and cargo test -p techscript_lexer to ensure no regressions were introduced. Note that pre-existing build failures in the workspace (due to dependency version issues) are unrelated to this change and do not block its success.
✨ Result: A safer, more maintainable codebase that leverages the compiler's dead code analysis capabilities for the lexer's token definitions.

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PR created automatically by Jules for task 4739434527682246520 started by @Tcode-Motion

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