Control plane + system index docs consolidated into one canonical doc
Eight superseded control-plane docs archived; replaced by CONTROL_PLANE_AND_SYSTEM_INDEX.md. Five source files repointed. CONTRACT_TO_CODE_TRACE_MATRIX.md held — validate-contract-trace.mjs reads it at runtime.
·HOLD: CONTRACT_TO_CODE_TRACE_MATRIX.md — validate-contract-trace.mjs sets TRACE_MATRIX_PATH to it at runtime; requires script rewrite before archiving