Match the file-preprocessor behaviour for live operator input. When a
Z-down jog or MDI line would push (A-Z) above the safe band, append
the matching A delta to the same line so the planner runs Z and A
together. Same direction-aware refusal: only error when the operator
explicitly asks A to move *up* (delta > 0) past the bound, or when
the required A would violate A's soft minimum.
Implementation:
* ExternalAxis.coordinate_mdi rewrites a multi-line MDI burst,
tracking G90/G91 modal across lines (jogs always emit
M70/G91/G0/M72; standard MDI defaults to G90). Z and A targets
are computed in machine coords using offset_z and offset_a so
the work-coord A token we emit is consistent with the operator's
frame.
* The 'A0' the jog UI emits for axes that aren't moving is treated
as 'no A intent' (G91 delta of zero) and freely overridden.
* Hooked into Mach.mdi after the existing ATC rewrite. On
ExternalAxisError the burst is dropped with a user message; the
planner check downstream still fires as defense in depth.
* Planner.__encode also catches ExternalAxisError now (vs
bricking on uncaught) - logs to the operator messages list and
halts the cycle cleanly so subsequent jogs work.
* check_coupling itself is now improvement-aware: only refuses
moves that worsen an existing violation. Pure XY jogs and
Z-up/A-down recovery moves pass even when (A-Z) is currently
above the bound.
Tested locally with synthetic MDI: small Z jog within band, Z jog
across the boundary (auto-injects A delta), G90 MDI G0 Z-50
(appends A106), explicit A-lift while Z deep (refuses), pure XY
jog (unchanged), G91 A-down (unchanged), G90 G0 A0 with
offset_a=134 (refuses as lift to home).
Henrik Muehe
683fa673ae