Normalize x-model boolean parsing for case and whitespace

[utsavsomaiya]

Summary

• normalize .boolean string parsing in safeParseBoolean by trimming whitespace and lowercasing before token checks
• keep existing fallback behavior for unknown/non-empty strings
• add Vitest coverage for mixed-case and whitespace-wrapped boolean tokens
• document .boolean matching behavior as case-insensitive and whitespace-tolerant

Why

Currently, values like " FALSE " are treated as truthy because string matching is exact. This change makes .boolean parsing more predictable for common user input.

Testing

• npm run vitest
• npm run build