fix(v4): the final review's six minors in the ROM boot

- Text after start is refused, as text.c refuses it: before it jumps, the
  ROM reads on to the end of the source; blanks, comments and the ends of
  blobs may follow, a token is ERR-AFTER (26), "text after start".
- A token too long where a name, a target or a value is wanted is "name
  too long", as text.c says: (MISSING) reports "missing" only when no error
  came first.  `", keeps "missing", which is text.c's word for both.
- text.c's "address out of range" names the address, not the value.
- The system's source files are one list, v4/sys_files.h: boot.c, the
  harness and the nucleus test are made from it.
- The ROM's error codes and words are one list, v4/rom_errors.h: boot.c's
  messages, host_map.h's ROM_ERR_* and mkmap's ERR-* are made from it.
- node.h says what v4_node_store does with a ROM address (nothing, as for
  any address outside RAM, D-14); test_host_rom_range pins it.

ROM: 2095 words, rom_hash 0x06d0dcb7a0cb41a1.  dict_hash unchanged,
0xe5a57f3eb72ff94a.  make -C v4 test test-32 hosted-check pass.  QEMU:
amd64, aarch64, riscv64 to ok>, POST 538/538, POST: PASSED.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

v4/include/v4/node.h

@@ -60,7 +60,9 @@
 /* THE ROM (docs/v4.0.0/MACHINE.md section 2, DATASHEET-F18.md section 5).
  * A read-only range of V4_ROM_WORDS words at V4_ROM_BASE, just above RAM.
  * An instruction fetch, an @p literal and a data fetch there read the ROM; a
- * running programme's store there is an address fault.  In the model it is
+ * running programme's store there is an address fault.  C code's
+ * v4_node_store there does nothing and counts no fault, as for any address
+ * outside RAM (D-14, at v4_node_store below).  In the model it is
  * attached, as every device is, and v4_node_reset detaches it: the owner
  * attaches it again after a reset.  The range's size is a build parameter,
  * as RAM's is; 0 (the default) is a machine with no ROM. */

v4/include/v4/rom_errors.h

@@ -0,0 +1,43 @@
+/* rom_errors.h -- the ROM's error codes and what they mean.
+ *
+ * The ROM (capsules/v4/rom) stops at (ROM-FAILED) with one of these codes in
+ * (FAILED); the loader, which owns the console, prints its words
+ * (v4/system/boot.c).  This is the one list: the map's constants ERR-* the
+ * ROM is assembled with (v4/tools/mkmap.c, through v4/tests/host_map.h's
+ * ROM_ERR_*) and the boot's messages are both made from it.  The codes run
+ * 1, 2, 3 ... in order; a new one goes at the end.
+ *
+ * X(NAME, CODE, WORDS)
+ */
+#ifndef V4_ROM_ERRORS_H
+#define V4_ROM_ERRORS_H
+
+#define V4_ROM_ERRORS(X) \
+    X(TOO_LONG,   1, "name too long")                                   /* a token longer than 63 characters */ \
+    X(COMMENT,    2, "comment not closed")                              /* a ( with no ) before the end of its blob */ \
+    X(BAD_NAME,   3, "cannot be used as a name")                        /* an opcode, a reserved word, a label, a number or &... */ \
+    X(DEFINED,    4, "already defined") \
+    X(NAMES,      5, "too many names")                                  /* the symbol table is full */ \
+    X(FIT,        6, "does not fit: memory is full, or a branch cannot reach") \
+    X(OPCODE,     7, "not an opcode the packer takes there") \
+    X(IN_MACRO,   8, "not allowed in a macro") \
+    X(MACRO,      9, "macro without endmacro, or endmacro without macro") \
+    X(LABEL_DUP, 10, "label already defined in this word") \
+    X(LABELS,    11, "too many labels in one word") \
+    X(FOR,       12, "FOR nested too deep, NEXT or UNEXT without FOR, or FOR without NEXT") \
+    X(UNEXT,     13, "FOR ... UNEXT must fit one instruction word and hold no literal") \
+    X(TARGET,    14, "not something to branch to") \
+    X(UNDEFINED, 15, "never defined") \
+    X(BIG,       16, "number does not fit a cell") \
+    X(AMP,       17, "& needs a word that is already defined") \
+    X(FETCH_P,   18, "write the number, not @p") \
+    X(MISSING,   19, "a name, a target, a value or a string is missing") \
+    X(DEEP,      20, "macros nested too deep") \
+    X(REFS,      21, "too many unresolved branches") \
+    X(VALUE,     22, "not a value") \
+    X(NO_START,  23, "the source ended with no start") \
+    X(START,     24, "start of something not a word") \
+    X(RANGE,     25, "address out of range")                            /* store outside RAM */ \
+    X(AFTER,     26, "text after start")
+
+#endif

v4/include/v4/sys_files.h

@@ -0,0 +1,17 @@
+/* sys_files.h -- the system's source, in the order the ROM reads it.
+ *
+ * capsules/v4/sys: the memory map (map-<cell bits>.f18) first, then these,
+ * then end.f18 -- the state the system is switched on in, and `start`.  The
+ * one list: the boot feeds these blobs (v4/system/boot.c), and the tests
+ * that build the system read these files (v4/tests/rom_harness.h).
+ *
+ * X(FILE): capsules/v4/sys/FILE.f18
+ */
+#ifndef V4_SYS_FILES_H
+#define V4_SYS_FILES_H
+
+#define V4_SYS_FILES(X) \
+    X(core) X(input) X(dict) X(codegen) X(compile) X(quit) X(forth) \
+    X(numout) X(words) X(system) X(qmath) X(blocks) X(log) X(acl)
+
+#endif