fix(v4): overlong lines are refused whole; a refused store moves neither A nor P

- hosted (v4/tools/hosted.c): a line longer than the buffer is read to its
  end and refused as too long. Before, fgets handed it over in 1025-byte
  pieces and the last piece ran as a line of its own.
- bare metal (kernel/src/v4/sk_v4.c): the line editor takes 1024
  characters, as the boot does, and a line typed past that is refused as
  too long instead of being cut at 255 and run. V4_BOOT_LINE_TOO_LONG is
  now reported at the prompt and while a line waits.
- engine (v4/src/exec.c): a store the node itself refuses (to "any port",
  "which port", How or Have) left the opcode running on: !+ advanced A,
  against node.h's FAULTS, and !p advanced P past the handler, into the
  next fault kind's entry. A refused store now does nothing more; a store
  that raises an error (D-18) still counts as made, but P stays the
  handler's.
- test_port.c: both cases; they fail on the old exec.c (A 1017, P 901).

Engine-level tests (all v4/tests/test_*.c but test_host_*) pass at 32 and
64 bits; test_port also under ASan/UBSan. Not yet run: make -C v4 test,
test-32, hosted-check, and the three QEMU acceptance boots.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GE3SDvQn5EoxdGufk84zz2

kernel/src/v4/sk_v4.c

@@ -29,7 +29,7 @@
 #include "v4/boot.h"
 #include "block_subsystem.h"
 
-#define SK_V4_LINE   255u                /* what the line editor here takes */
+#define SK_V4_LINE   1024u               /* what the line editor here takes: a line, as the boot takes one (v4/system/boot.c) */
 
 /* v3's prompt (repl.c's SK_PROMPT_TEXT): "ok> " in bright cyan, after the
  * console's own "[zuse@Hera] " line prefix. */
@@ -82,12 +82,15 @@ static void sk_v4_serve(v4_node *node, unsigned request)
  * Zuse's session has ended (her drive was pulled): the caller goes headless
  * (not in a build with EMERGENCY_CONSOLE_ENABLED, whose console needs no
  * login: v3's sk_console_readline() the same).  While nothing is typed the
- * idle beat runs, as v3's. */
+ * idle beat runs, as v3's.  A line typed past SK_V4_LINE characters is not
+ * cut short and run: what is typed after that is not kept, and
+ * SK_V4_LINE + 1 is returned, which the boot refuses as too long
+ * (V4_BOOT_LINE_TOO_LONG), running nothing. */
 #define SK_V4_CURSOR_BLINK 50u           /* ticks between blinks, as v3's (500 ms at 100 Hz) */
 
 static int sk_v4_readline(void)
 {
-    int len = 0;
+    int len = 0, over = 0;
     int cursor_on = 1;
     uint64_t blink = heartbeat_ticks();
 
@@ -113,11 +116,16 @@ static int sk_v4_readline(void)
             arch_relax();
             continue;
         }
-        if (c == '\r' || c == '\n') { console_fb_erase_cursor(); console_putc('\n'); return len; }
+        if (c == '\r' || c == '\n') {
+            console_fb_erase_cursor(); console_putc('\n');
+            return over ? (int)SK_V4_LINE + 1 : len;
+        }
         if (c == 8 || c == 127) {
-            if (len > 0) { len--; console_putc(8); console_putc(' '); console_putc(8); }
-        } else if (c >= 32 && c < 127 && len < (int)SK_V4_LINE) {
-            sk_v4_text[len++] = (char)c;
+            if (over > 0) { over--; console_putc(8); console_putc(' '); console_putc(8); }
+            else if (len > 0) { len--; console_putc(8); console_putc(' '); console_putc(8); }
+        } else if (c >= 32 && c < 127) {
+            if (len < (int)SK_V4_LINE) sk_v4_text[len++] = (char)c;
+            else over++;
             console_putc((char)c);
         }
         cursor_on = 1;                           /* typing shows a solid cursor, as v3's */
@@ -196,6 +204,7 @@ void sk_v4_run(void (*chain)(void), const BootDisk *boot_disk)
                 break;
             }
             how = v4_boot_line(&boot, sk_v4_text, (unsigned)len);
+            if (how == V4_BOOT_LINE_TOO_LONG) { console_puts("Line too long\n ERROR\n"); how = V4_BOOT_LINE_WAITING; continue; }
             if (how == V4_TEXT_ERROR) console_puts(" ERROR\n" SK_V4_PROMPT);
             else if (how == V4_TEXT_COMPLETED) console_puts(" ok\n" SK_V4_PROMPT);
             else break;
@@ -204,6 +213,7 @@ void sk_v4_run(void (*chain)(void), const BootDisk *boot_disk)
         if (logged_out && (how == V4_TEXT_ERROR || how == V4_TEXT_COMPLETED)) continue;
         if (how == V4_TEXT_COMPLETED) console_puts(" ok\n");
         else if (how == V4_TEXT_ERROR) console_puts(" ERROR\n");
+        else if (how == V4_BOOT_LINE_TOO_LONG) console_puts("Line too long\n ERROR\n");
         else if (how == V4_BOOT_LINE_REFUSED) console_puts("Message refused\n ERROR\n");      /* the node's wire is full: error 19's words */
         else if (how == V4_BOOT_LINE_STOPPED) {
             console_println("StarForth v4: the node stopped on a fault");