Adds rot13 to the variantSet built in scanForInjection(), so
imperative phrases hidden as rot13 inside code comments still hit
the existing CRITICAL/HIGH/MEDIUM pattern arrays.
normalizeForScan() already covers base64, hex, URL, and HTML decoding
in a 3-iteration loop — those are NOT duplicated here. rot13 is the
only genuinely new variant: it is its own inverse and not part of any
NIST/Unicode normalization spec, so it has to be applied explicitly.
Threshold: only inputs >40 chars enter the rot13 pass, to suppress
false positives on accidental letter-shifts in tokens, ids, and short
identifiers. Variants are deduplicated against the existing set so
matchers do not run twice.
3 new tests in injection-patterns.test.mjs (rot13 detection, sub-40
char suppression, plaintext path still green). Total 168 tests pass.
Closes E3 in critical-review-2026-04-20.md.
950e4e4bce