Fix misleading machine state information after program abort

[Sigma1912]

This fixes issues #2745 and #2908 and adds clarification to the documentation

The current situation of not resetting the controller after a program abort leaves parameter values and the status channel out of sync. This causes the DRO to display wrong information about axis position and offset values after a program abort.
The new default behavior (if no [RS274NGC] ON_ABORT_COMMAND entry is found in the ini file) is to issue 'M2' on a program abort which correctly resets and synchronizes the parameter values and the status channel.

[BsAtHome]

The patch fails these tests:

• tests/abort/feed-rate
• tests/motion-logger/basic
• tests/motion-logger/startup-gcode-abort
• tests/statbuffer-g5x-abort

Are these side effects or problems?

[Sigma1912]

Oh my, I forgot the tests. I'll need to have a look at those.
Thanks.

[Sigma1912]

I get these results:

Runtest: 260 tests run, 255 successful, 4 failed + 1 expected, 1 skipped
Failed: 
	/home/user/git/mylinuxcnc-repo/tests/abort/feed-rate
	/home/user/git/mylinuxcnc-repo/tests/motion-logger/basic
	/home/user/git/mylinuxcnc-repo/tests/motion-logger/startup-gcode-abort
	/home/user/git/mylinuxcnc-repo/tests/statbuffer-g5x-abort

This expects the feed-rate to remain unchanged but with this PR feed-rate is reset to zero

Running test: /home/user/git/mylinuxcnc-repo/tests/abort/feed-rate
*** /home/user/git/mylinuxcnc-repo/tests/abort/feed-rate: XFAIL: test run exited with 1

With this PR an abort resets spindle-synchronisation.

Running test: /home/user/git/mylinuxcnc-repo/tests/interp/m98m99/12-M99-endless-main-program
--- expected.motion-logger	2025-06-04 12:39:47.413552065 +0200
+++ out.motion-logger	2025-06-04 14:35:39.697162112 +0200
@@ -192,6 +192,7 @@
 ENABLE_AMPLIFIER
 ENABLE_AMPLIFIER
 ENABLE_AMPLIFIER
+SET_SPINDLESYNC sync=0.000000, flags=0x00000000
 COORD
 JOG_ABORT joint=0
 JOG_ABORT joint=1
*** /home/user/git/mylinuxcnc-repo/tests/interp/m98m99/12-M99-endless-main-program: XFAIL: checkresult exited with 1

With this PR an abort resets spindle-synchronisation.

Running test: /home/user/git/mylinuxcnc-repo/tests/motion-logger/basic
*** /home/user/git/mylinuxcnc-repo/tests/motion-logger/basic: XFAIL: test run exited with 1
Running test: /home/user/git/mylinuxcnc-repo/tests/motion-logger/mountaindew
Running test: /home/user/git/mylinuxcnc-repo/tests/motion-logger/startup-gcode-abort
--- expected.motion-logger	2025-06-04 14:42:04.769566055 +0200
+++ out.motion-logger	2025-06-04 14:42:06.382454724 +0200
@@ -109,3 +109,5 @@
 JOG_ABORT joint=15
 ABORT
 SPINDLE_OFF
+SET_SPINDLESYNC sync=0.000000, flags=0x00000000
+SPINDLE_OFF
*** /home/user/git/mylinuxcnc-repo/tests/motion-logger/startup-gcode-abort: XFAIL: checkresult exited with 1

This expects the work offset system to remain unchanged but with this PR work offset is reset to default g54

Running test: /home/user/git/mylinuxcnc-repo/tests/statbuffer-g5x-abort
*** /home/user/git/mylinuxcnc-repo/tests/statbuffer-g5x-abort: XFAIL: test run exited with 1

Seeing this I feel that this PR cannot be merged into 2.9 and would seem to require discussion about changing abort behavior in general even in master.
Personally I would argue that retaining such settings as feed-rate, work-offset, spindle-synchronization and possibly other things doesn't really make sense on a program-abort event.
It may however be an advantage when using MDI.
Maybe another fix for the mentioned issues can be found.

[Sigma1912]

After some more testing I've decided to reopen this as a draft for discussion.

The current default behavior on abort during a gcode program ending in 'm2' or 'm30' is just crazy. Not even the displayed axis positions can be trusted let alone any of the displayed active gcodes. G92/G52 offset values in the offset pages are showing zeros when the actually applied offset is non-zero.

[andypugh]

It is probably worth asking for discussion on the developers mailing list.

[Sigma1912]

Not a viable fix as the 'm2' would also be executed on program stop and faulty mdi commands.