Double CosmOS's half of the machine, and check that it fits

The memory map gave CosmOS 0x0000 through 0x1FFF of Program Memory and
applications 0x2000 and above. CosmOS is 8141 bytes at the previous commit,
which is fifty one bytes short of the line, and the next thing added to it
went over.

GOING OVER DOES NOT FAIL WHERE IT HAPPENS. Nothing enforces the division: an
application says where it goes with #Base and the loader puts it there, so a
CosmOS that has grown past 0x1FFF simply has the next program loaded written
over the end of it. What breaks is whichever part of the shell that program
happened to cover, at whatever later moment somebody uses it. It turned up here
as the monitor's assemble command answering "I do not know" to valid
instructions, several commands into a session, on a machine that had booted
perfectly well.

Both halves are doubled: applications now start at 0x4000 in Program Memory and
0x2000 in Data Memory. That is 16K of code and 8K of data for the system,
against the 8775 and 2948 it uses today. Both were on the same trajectory, and
moving them together means the twenty files that say #Base are edited once
rather than twice.

The standalone loader's loadable.asm keeps its old base: it belongs to the
loader CosmOS grew out of, not to CosmOS, and its addresses answer to a
different program. The unbased-segment diagnostic keeps its old base too - it
exists to produce an error message that names the address, and the message is
what is recorded.

Tests/docs.sh now reads the two limits out of the table in the README and
measures both segments against them. It reads them rather than being told them
because the table is the specification, and this is the second time in this
project that the thing nobody checked is the thing that rotted.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW

Tests/expected/cosmosMonitor.out

@@ -2,25 +2,25 @@ CosmOS
 > x examine, d disassemble, a assemble, s set, b bank, g go, exit leaves
 * b <program|data|number>
 * there is no such bank
-* loaded, starting at 2000
+* loaded, starting at 4000
 * bank 00
-* 2000  47 00 10 00  SETD.0 1000
-2004  18 10        SWI 10
-2006  47 00 10 44  SETD.0 1044
-200A  18 10        SWI 10
-200C  47 00 10 7A  SETD.0 107A
-2010  27 1F        INIB 1F
-2012  18 11        SWI 11
-2014  47 00 10 5D  SETD.0 105D
-* 2000  47 00 10 00 18 10 47 00 10 44 18 10 47 00 10 7A  G.....G..D..G..z
-2010  27 1F 18 11 47 00 10 5D 18 10 47 00 10 7A 18 10  '...G..]..G..z..
-2020  47 00 10 65 18 10 18 12 00 00 00 00 00 00 00 00  G..e............
-2030  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
+* 4000  47 00 20 00  SETD.0 2000
+4004  18 10        SWI 10
+4006  47 00 20 44  SETD.0 2044
+400A  18 10        SWI 10
+400C  47 00 20 7A  SETD.0 207A
+4010  27 1F        INIB 1F
+4012  18 11        SWI 11
+4014  47 00 20 5D  SETD.0 205D
+* 4000  47 00 20 00 18 10 47 00 20 44 18 10 47 00 20 7A  G. ...G. D..G. z
+4010  27 1F 18 11 47 00 20 5D 18 10 47 00 20 7A 18 10  '...G. ]..G. z..
+4020  47 00 20 65 18 10 18 12 00 00 00 00 00 00 00 00  G. e............
+4030  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
 * bank 01
-* 1000  61 20 70 72 6F 67 72 61 6D 2C 20 6C 6F 61 64 65  a program, loade
-1010  64 20 6F 66 66 20 61 20 64 69 73 6B 2C 20 72 75  d off a disk, ru
-1020  6E 6E 69 6E 67 20 6F 6E 20 74 68 65 20 73 79 73  nning on the sys
-1030  74 65 6D 20 74 68 61 74 20 6C 6F 61 64 65 64 20  tem that loaded 
+* 2000  61 20 70 72 6F 67 72 61 6D 2C 20 6C 6F 61 64 65  a program, loade
+2010  64 20 6F 66 66 20 61 20 64 69 73 6B 2C 20 72 75  d off a disk, ru
+2020  6E 6E 69 6E 67 20 6F 6E 20 74 68 65 20 73 79 73  nning on the sys
+2030  74 65 6D 20 74 68 61 74 20 6C 6F 61 64 65 64 20  tem that loaded 
 * bank 02
 * 0000  01 FF 00 00 00 00 00 00 01 FF 00 00 00 00 00 00  ................
 0010  03 FF 08 00 00 00 00 00 01 20 01 00 00 00 00 00  ......... ......