Fixed assembler bug that caused crash on IR array resize. Added line editor app.

README.md

@@ -110,6 +110,10 @@ Disk images that tests read from are built by Tests/makedisks.sh before the run,
 
 The disk tool is checked separately by Tests/disk.sh, which make test runs afterwards: it puts files of every awkward size onto an image and takes them off again, and checks that the things the format says cannot happen are refused.
 
+Tests/terminal.sh checks the things a recorded output cannot see. Every other test pipes input in and output to a file, which answers what a program prints and is blind to two whole classes of behaviour: **when** something is printed, since piped output is buffered and flushed at exit, so a prompt shown before its answer is asked for and one shown an hour late produce identical files; and **what happens to the terminal**, since key mode only touches one when there is one. Both have gone wrong here, and both were found by a person whose terminal stopped working rather than by anything in this suite. So it runs the emulator under a pseudo-terminal and asks the questions directly: that a prompt arrives before input is read, that a keystroke arrives without Return, that the terminal is handed back however the machine dies, and that suspending and resuming leave it as they found it.
+
+A cycle count is deliberately **not** part of a recorded result. The last line of the emulator's output has the number taken out of it before anything is compared, keeping only whether the program stopped on its own or ran into its limit, which is behaviour. Two instructions added to CosmOS used to move that number in six unrelated files at once, so a real difference would arrive in a crowd of meaningless ones. Anything that wants to measure cycles should say so in a test of its own.
+
 Tests/docs.sh then checks the manuals against the code: that every instruction has a row and every row is an instruction, that the counts in the headings are right, that every directive is written down, that every routine the manuals promise exists, and that the worked examples still assemble to the bytes printed beside them. Documentation goes stale quietly, and this is what stops it.
 
 Tests are defined in Tests/manifest, one line per program. To record the current output as the expected result, after you have checked that it is correct: