test: add edge case coverage for input parsing

[CreeptoGengar]

Describe your changes

Adds test coverage for edge cases in input file parsing to improve robustness and document expected behavior for boundary conditions.

Added tests:

• test_parse_word_too_long_hex() - validates error handling for hex strings longer than 64 characters
• test_parse_word_invalid_hex_characters() - validates error handling for invalid hex characters (g, h, z)
• test_parse_stack_inputs_large_numbers() - validates handling of large numbers in operand_stack (u64::MAX, Felt::MODULUS - 1, Felt::MODULUS)
• test_parse_advice_stack_large_numbers() - validates handling of large numbers in advice_stack
• test_parse_advice_map_duplicate_keys() - documents behavior when duplicate keys are present in advice_map (HashMap silently overwrites)

[github-actions]

Automated check (CONTRIBUTING.md)

Findings:

• Link an issue in the PR body (e.g., "Fixes Implement SHA256 in Miden Assembly #123").
• Add a short Rationale explaining why the change is needed.

Recommendations:

• Consider adding a Test plan or clear review steps.

Next steps:

• Link a relevant issue (e.g., "Fixes Implement SHA256 in Miden Assembly #123") and ensure it is assigned to you.
• See CONTRIBUTING.md for expectations.
• If this is a false positive, comment: /quality-review.

[bobbinth]

Thank you, but we do not accept PRs without associated issues.