Description

Adds detectTruncation(), a new public API that analyzes TOON input and
returns a structured report about missing items, without throwing exceptions.

Closes #312

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test coverage improvement

Changes Made

• packages/toon/src/index.ts - adds detectTruncation()
• packages/toon/src/types.ts - adds TruncationReport and TruncatedArray types
• packages/toon/test/truncation.test.ts - 9 tests

Testing

• 9 new tests covering complete, truncated, and edge cases

• 466/466 existing tests still pass

• All existing tests pass

• Added new tests for changes

• Tests cover edge cases and spec compliance

Pre-submission Checklist

• My code follows the project's coding standards
• I have run code formatting/linting tools
• I have added tests that prove my fix/feature works
• New and existing tests pass locally
• I have updated documentation if needed
• I have reviewed the TOON specification for relevant sections

Breaking Changes

• No breaking changes
• Breaking changes (describe migration path below)

API

const report = detectTruncation('employees[100]{id,name}:\n  1,Alice\n  2,Bob')
// {
//   isTruncated: true,
//   arrays: [{
//     key: 'employees',
//     declaredCount: 100,
//     actualCount: 2,
//     missingItems: 98,
//     completionRate: 0.02
//   }]
// }