v0.16.3

Fixes a crash in token-value extraction while keeping the existing vectorized tokenizer scan. Notably does NOT ship the experimental linear rewrite (perf/tokenizer-linear): sigil 0.17.15's native char-iteration lifted the old scan's dominant cost (per-token make-string/string-set!), which made the linear rewrite a 1.2-1.7x REGRESSION vs the old scan, so it is archived rather than shipped. Differential tests pass; 8k-line tokenize ~1785ms (old-scan speed) with the crash fix.