fix: backspace printing + clean a few warnings/junk code

src/drivers/keyboard.c

@@ -1,9 +1,6 @@
 #include "keyboard.h"
 #include "drivers.h"
 #include "interrupts.h"
-#include "kprintf.h"
-#include "shell.h"
-#include "string.h"
 #include "terminal.h"
 #include <stdbool.h>
 #include <stdint.h>
@@ -15,13 +12,13 @@ static struct key_event new_input = {};
 
 void keyboard_handler(struct registers *regs)
 {
+	(void)regs;
 	new_input_indicator = true;
 	new_input = terminal_getkey();
 }
 
 struct key_event get_key(void)
 {
-
 	while (!new_input_indicator)
 		;
 	new_input_indicator = false;

src/shell/exec.c

@@ -82,14 +82,15 @@ static char *get_line(void)
 
 	while (1) {
 		ev = get_key();
-		// kprintf("%d %d\n", ev.scan_code, ev.c);
 		if (ev.c == '\n')
 			break;
 		char *buf = screen->line;
 		i = strlen(screen->line);
 		const size_t size = sizeof(screen->line);
 		if (ev.scan_code) {
-			if (ev.scan_code == KEY_BACKSPACE && i) {
+			if (ev.scan_code == KEY_BACKSPACE) {
+				if (!i)
+					continue;
 				buf[--i] = '\0';
 				move_cursor(LEFT);
 				terminal_putchar(' ');
@@ -106,6 +107,7 @@ static char *get_line(void)
 	}
 	kprintf("\n");
 	screen->line[i] = '\0';
+	return screen->line;
 }
 
 void shell_init()