fixed expected() logic

[ehwan]

No description provided.

[Copilot]

Pull Request Overview

This PR fixes the logic in the expected() method for both deterministic and nondeterministic parser contexts. The fix addresses how the parser handles state stack operations when determining expected tokens.

• Refactored expected_token_impl to use a separate extra_state_stack instead of modifying the original state stack
• Updated parameter handling to properly track stack lengths and node positions
• Implemented recursive token expectation logic that correctly handles reduce operations

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
rusty_lr_core/src/parser/nondeterministic/context.rs	Updated expected token implementation to use node-based stack tracking with proper reduce operation handling
rusty_lr_core/src/parser/deterministic/context.rs	Refactored to use separate extra state stack and stack length tracking for cleaner state management

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