Closes deferred Phase-9 item 8. Phase 9 promoted realIP / lastNonEmptyXFF /
OptionalHeader to internal/middleware and refactored webbug only; the
other generators kept their byte-identical local copies. Sweeping them
all over now while the touch surface is already open for Phase 10.
- docx, envfile, kubeconfig, pdf, slowredirect: drop the local
realIP / lastNonEmptyXFF / optionalHeader functions plus the
CF-Connecting-IP / X-Forwarded-For / X-Real-IP header constants.
Trigger paths now call middleware.RealIP / middleware.OptionalHeader
directly. Drops the unused "net" import from each.
- slowredirect/fingerprint_handler.go: same treatment for the
AttachFingerprint call site.
No behavior change — middleware.RealIP is byte-identical to what was
previously inlined per generator; verified by re-running the per-package
trigger tests post-refactor.
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