fix: Blitter UART divisor 234→233 to match Lean uartBaudDivisor proof

Both now 115384 baud at 27MHz (within 0.16% of 115200).
Lean theorem uartBaudRateHz_within_1pct_of_115200 applies to both.

4-Infrastructure/hardware/Blitter6502OISC_small.v

@@ -233,7 +233,7 @@ module Blitter6502OISC (
     reg [9:0] uart_shift;
     reg uart_active;
 
-    localparam UART_DIV = 16'd234;  // ~115200 baud at 27MHz
+    localparam UART_DIV = 16'd233;  // 115384 baud at 27MHz (matches Lean uartBaudDivisor)
 
     always @(posedge clk or negedge rst_n) begin
         if (!rst_n) begin