CVE-2026-62866: Dasel: Selector lexer panics on trailing whitespace in `parseCurRune`

Same panic class as GHSA-m5j3-4634-c2vq and GHSA-m6xr-fvfg-5g64, sister site on the same function. Trigger is any selector ending in whitespace: dasel query 'a ' panics at selector/lexer/tokenize.go:60.

The whitespace-skip loop right above (lines 55-57) advances p.i to p.srcLen when the input is all-whitespace or whitespace-trailing. The very next line reads p.src[p.i] without a bounds check.