🧹 [code health] Remove unused lexer code allowance

[Tcode-Motion]

🎯 What: Removed the unnecessary #[allow(dead_code)] attribute from the LogosToken enum in compiler/lexer/src/lib.rs.
💡 Why: The enum variants are actively used (generated by logos-derive and mapped exhaustively in Lexer::map_logos_token). Removing the dead code allowance cleans up the code and ensures that if variants are ever actually unused in the future, the compiler will catch it, improving maintainability.
✅ Verification: Ran RUSTFLAGS="-D warnings" cargo check --workspace and cargo test --workspace to confirm that removing the attribute did not introduce any compilation warnings or errors, and all tests pass.
✨ Result: Improved code cleanliness and stricter compilation checks for the lexer crate.

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PR created automatically by Jules for task 13170916467475915447 started by @Tcode-Motion

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