Decouple functions.c from interpreter array-LHS private state [Coupling]

functions.c::_op_assign() was reading p_interpret->p_token_array_lhs and
p_interpret->i_array_lhs_index directly — a hidden cross-module coupling
where the functions module reached into interpreter-private state.

Pass the array-LHS context as explicit parameters instead:
- _op_assign() gains Token *p_array_lhs, int i_lhs_idx params
- _process() propagates them to _op_assign()
- function_process() propagates them from the call site

In interpret.c the "restore" lines that set p_interpret->p_token_array_lhs
and p_interpret->i_array_lhs_index before calling function_process() are
removed; instead p_lhs and i_lhs_idx are passed directly. The three
non-array-LHS call sites pass NULL / 0. _op_assign() no longer touches
Interpret internals for the array assignment path.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/src/core/functions.h b/src/core/functions.h
index e20355b..ac45d5e 100644
--- a/src/core/functions.h
+++ b/src/core/functions.h
@@ -50,9 +50,11 @@ Functions* functions_new();
 void functions_delete(Functions *p_functions);
 void functions_init(Functions *p_functions);
 
+/* p_array_lhs / i_lhs_idx carry array-element LHS context for arr[i] = val;
+ * pass NULL / 0 for plain assignment or non-assignment operators. */
 void function_process(Interpret *p_interp, Token *p_token_op,
                       Token *p_token_op2, Stack *p_stack_args,
-                      int i_args);
+                      int i_args, Token *p_array_lhs, int i_lhs_idx);
 _Bool function_is_buildin(Token *p_token_ident);
 void function_process_buildin(Interpret *p_interpret,
                               Token *p_token_ident,