Remove %trace directive and runtime tracing functionality

[ehwan]

Description

This PR removes the %trace directive, the is_trace trait method, and the context.trace() runtime diagnostics from the parser core and generator.

Motivation

The %trace option has seen little practical utility for parsing diagnostics in standard applications. Furthermore, marking non-terminals with %trace prevents the optimization engine from applying key optimizations (such as Unit Production Elimination), resulting in larger parser tables and binary sizes. Removing %trace simplifies the codebase and allows more aggressive optimizations across all non-terminal symbols.

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Key Changes

1. rusty_lr_core (Runtime)

• Removed the is_trace method from the NonTerminal trait in nonterminal.rs.
• Removed pub fn trace(&self) and associated helper implementations from both the deterministic (deterministic/context.rs) and nondeterministic (nondeterministic/context.rs) parser contexts.

2. rusty_lr_parser (Parser Generator)

• Removed parsing support for the %trace directive in parser.rs and the Lexed::Trace token type in lexer.rs.
• Removed code generation logic for the is_trace trait implementation in emit.rs.
• Cleaned up the NonTerminalInfo struct to remove the trace field, updating all initializations in grammar.rs and pattern.rs.

3. Bootstrap & Testing

• Regenerated parser_expanded.rs and the regression diff files (calculator.rs, calculator_u8.rs, json.rs) with the updated compiler.

4. Documentation

• Removed references and examples of context.trace() from README.md.
• Removed the "Tracing Non-Terminals" section and corresponding TOC entry in SYNTAX.md.

[gemini-code-assist]

Code Review

This pull request removes the %trace feature and its associated functionality across the codebase. This includes removing the trace method from both deterministic and nondeterministic parser contexts, deleting the is_trace method from the NonTerminal trait, and cleaning up the parser, lexer, grammar definitions, and documentation that supported tracing non-terminals. I have no feedback to provide as there are no review comments.

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