add IntermediateState for lightweight state generation

[ehwan]

this could reduce binary size by 10%

we were using builder::State for state generation which was using BTreeMap.
add new IntermediateState struct for common type convertion into any parser state type, and it is using Vec.

[Copilot]

Pull Request Overview

This PR introduces a new IntermediateState struct to serve as a lightweight intermediate representation for state generation in the LR parser. The change refactors the code generation and state conversion pipeline to use Vec instead of BTreeMap/BTreeSet collections for better performance during code generation.

Key changes:

• Introduces IntermediateState struct with Vec-based fields for shift/goto maps and reduce rules
• Replaces BTreeMap/BTreeSet usage with Vec in code generation
• Updates conversion logic to handle sorted vector extraction instead of map key removal

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 4 comments.

File	Description
rusty_lr_parser/src/emit.rs	Updates code generation to use IntermediateState and Vec collections instead of BTreeMap/BTreeSet
rusty_lr_core/src/parser/state.rs	Adds IntermediateState struct and updates conversion logic to handle vector-based state representations
rusty_lr_core/src/builder/state.rs	Adds conversion from builder State to IntermediateState

Comments suppressed due to low confidence (1)

[Copilot]

The sorting requirement is critical for correctness but only mentioned in comments. Consider adding runtime assertions or using a type that enforces this invariant.

[Copilot]

The hardcoded TerminalSymbol::Term(0) in the assertion makes assumptions about the type parameter. Consider using a more generic approach or documenting this constraint.

Suggested change

	debug_assert!(
	TerminalSymbol::Term(0) < TerminalSymbol::Error
	&& TerminalSymbol::<i32>::Error < TerminalSymbol::Eof
	);
	// Removed hardcoded assertion about TerminalSymbol ordering to avoid assumptions about type parameter.

[Copilot]

Duplicate assertion logic exists in both SparseState and DenseState conversion methods. Consider extracting this into a shared validation function.