docs(rfc): correct additive-field workflow and clean up non-ASCII punctuation

Replace the stale 'extend the maximal vector' loop with the frozen-maximal /
growing-probe workflow, and state which steps are hard CI gates (mandatory tag,
projectV1 emission probe) versus the recommended-but-ungated golden vector.

Also replace horizontal-ellipsis characters with ASCII '...' and one stray
loanword accent; intentional diagram/math notation is left as-is.

Author: dmcilvaney