Implement SWI 0x13 for 4-bit and 8-bit symbols. Traverse forward-offset trees using MSB-first input words and pack symbols into complete output words. Validate visited edges, leaf widths, alignment, output lengths, and address bounds.
Add 21 regression tests with independent tree serialization and path encoding, deep/max-size trees, word-boundary refills, malformed input, partial failures, caller state, and DMA/IRQ progress. Validate 656 default and 645 core-only tests in debug and release, plus all 10 native Darwin ARM64 window smoke tests.
