docs(config): VAR_DEPENDENCIES replaces VAR_ORDER

Each row lists every input the expression uses, physical columns and derived
variables alike.  No sequence number to maintain; statements are emitted in
dependency order and a cycle is rejected.

docs/tables/mpe_derived.md

@@ -17,7 +17,7 @@ The table is itself registered in [MPE_TABLES](/tables/mpe_tables/), so it is ma
  - 🔑 `LIBREF char(8)`: The libref of the target table
  - 🔑 `DSN char(32)`: The target table
  - 🔑 `VAR_NM char(32)`: The name of the derived column
- - `VAR_ORDER num`: Evaluation order; a variable may reference one with a lower order
+ - `VAR_DEPENDENCIES char(4000)`: Every input the expression uses - physical columns and derived variables, space separated
  - `VAR_TYPE char(1)`: `C` for character, `N` for numeric
  - `VAR_LEN num`: Character length, or numeric length (1-8)
  - `VAR_FMT char(32)`: Optional SAS format, eg `DATE9.`