Address customer feedback on signature field layout issues:
- Added truncation logic in `PDFBurner.vb` to limit text length
based on per-field maximums, appending a suffix (e.g., `..`).
- Enhanced `PDFBurnerParams.vb` with `TextMaxLengths` and
`TruncationSuffix` for configurable truncation behavior.
- Improved spacing and layout handling for signature fields to
prevent text collisions within fixed dimensions.
- Updated `EnvelopeGenerator.sln` with documentation for the
signature formatting fix (`fix-signature-field-formatting.md`).
- Applied truncation consistently across `AddFormFieldValue`
overloads and ensured deterministic rendering of annotations.