Unify command tokens: remove TK_COMMAND_INTERP and TK_INTERACTIVE_INTERP

Use cmd_mode (already on LexState) to signal whether interpolation
follows, instead of separate *_INTERP token variants. This eliminates
duplicate simple/interpolated code paths in the parser — commandexp()
and interactivestat() now each use a single unified loop that checks
cmd_mode != 0. A shared parseinterp() helper handles each ${expr}
interpolation cycle.

llex.c

@@ -50,8 +50,8 @@ static const char *const luaX_tokens [] = {
     "//", "..", "...", "==", ">=", "<=", "~=",
     "<<", ">>", "::", "<eof>",
     "<number>", "<integer>", "<name>", "<string>",
-    "<command>", "<command_interp>", "<envvar>",
-    "<interactive>", "<interactive_interp>"
+    "<command>", "<envvar>",
+    "<interactive>"
 };
 
 
@@ -475,8 +475,8 @@ static void read_string (LexState *ls, int del, SemInfo *seminfo) {
 ** Called initially when '`' is seen, and also continued via
 ** luaX_readcommandcont() after the parser processes an interpolated
 ** expression.
-** Returns TK_COMMAND if the string is complete (closing ` found),
-** or TK_COMMAND_INTERP if an interpolation ${...} was found.
+** Returns TK_COMMAND or TK_INTERACTIVE in all cases.
+** When an interpolation ${...} is found, cmd_mode remains non-zero.
 */
 static int read_command_body (LexState *ls, SemInfo *seminfo) {
   int interactive = (ls->cmd_mode == 2);
@@ -513,7 +513,7 @@ static int read_command_body (LexState *ls, SemInfo *seminfo) {
           seminfo->ts = luaX_newstring(ls, luaZ_buffer(ls->buff),
                                            luaZ_bufflen(ls->buff));
           ls->saved_cmd_mode = ls->cmd_mode;  /* save for readcommandcont */
-          return interactive ? TK_INTERACTIVE_INTERP : TK_COMMAND_INTERP;
+          return interactive ? TK_INTERACTIVE : TK_COMMAND;
         }
         else {
           save(ls, '$');  /* not an interpolation, keep literal '$' */