🧪 Add tests for validate_text edge cases in model.rs

[undivisible]

🎯 What: The testing gap addressed was missing edge case tests for validate_text in src/model.rs. The function is crucial to ensure we don't save empty strings and whitespace strings.
📊 Coverage: Test coverage was added for happy paths (valid strings without whitespaces, valid strings with leading/trailing/inner whitespaces, single character string) and error conditions (empty string, strings with only spaces, tabs, and newlines).
✨ Result: Increased test coverage for model.rs validation limits and increased reliability and safety of codebase by properly validating empty inputs.

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PR created automatically by Jules for task 15305117794027629981 started by @undivisible

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Note

Low Risk
Test-only changes with no runtime or validation logic modifications.

Overview
Adds two unit tests in model.rs that exercise validate_text directly, beyond the existing ClaimEvidence::validate cases.

test_validate_text_valid checks that non-empty strings pass, including leading/trailing whitespace and a single character. test_validate_text_invalid checks that empty and whitespace-only inputs (spaces, tabs, newlines, and mixed) return ValidationError::EmptyText with the supplied field name.

No production code changes—only test coverage for the trim-and-reject-empty behavior used by string ID construction and claim-evidence validation.

^{Reviewed by Cursor Bugbot for commit b4e0fd4. Configure here.}

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