VENUS-149 impersonation-guard: comment-stripper failing open on unbalanced regex-literal quote

VENUS-149 impersonation-guard coverage test was failing open for ~560 lines in admin-actions.ts. Comment-stripper had no regex-literal handling; a lone quote in an HTML escaper at line ~1630 opened a string it never closed, so // and /* */ stopped being recognised for the rest of the file. Any write token merely NAMED in a comment down there would have counted as a real write, and the scanner could not be trusted on that tail either way. Surfaced only because VENUS-372's addMissingParticipant was the first mutating export added after that line. Fixed in the same commit (7644158, v1.15.0) with regex-literal awareness + 3 regression tests. First regression fixture attempt passed with the defect still present (quotes rebalanced by luck) - rewritten to carry an odd quote count and assert comment-blindness specifically. Audited: no pre-existing violations were hidden behind it, tail exports all guard correctly.