nabla 0.7.1

CRAN resubmission release addressing reviewer feedback:

• Remove all commented-out code from @examples sections (inline expected-value comments and standalone comment lines)
• Quote technical terms in DESCRIPTION, add inst/WORDLIST for spell checker
• Save/restore par() in all vignette plotting chunks
• Replace <<- usage in vignettes/tests with explicit environment-based collection

Full R CMD check passes with 0 errors, 0 warnings, 1 NOTE (new submission).