fix(engine): publish the nozzle group result for sequential prints

The Print-level LayeredNozzleGroupResult had a single producer, the
by-layer branch of ToolOrdering, which is gated to non-sequential prints.
The by-object branch in Print::process computed a grouping only in auto
map modes and never stored it, so a sequential slice exported with a null
group result: the per-nozzle placeholder tables came up empty and any
start g-code indexing nozzle_diameter_at_nozzle_id[] aborted with
"Indexing an empty vector variable". A prior by-layer slice masked the
bug by leaving its (never cleared) result on the Print.

Now the by-object branch runs get_recommended_filament_maps in every
static map mode (in manual modes the result mirrors the user's
assignment, deviations throw as in by-layer) and publishes it
print-wide. The config write-back stays gated to auto modes: in manual
modes it would only re-store the pre-slice values.

Regression test: a two-object by-object print must publish a non-null
group result and resolve nozzle_diameter_at_nozzle_id[] in start g-code
(both fail without the fix). Suites green (libslic3r 48929/162,
fff_print 633/60); 18-fixture byte gate identical; the by-object repro
project goes from the export error to valid g-code, determinism x2.

src/libslic3r/GCode.cpp

@@ -8473,8 +8473,8 @@ std::string GCode::retract(bool toolchange, bool is_last_retraction, LiftType li
 
 void GCode::update_layer_related_config(int layer_id){
     auto group_result = m_print->get_layered_nozzle_group_result();
-    // Orca: sequential (by-object) prints never publish a Print-level layered group result on
-    // this branch; the statically applied config maps stay authoritative there.
+    // Orca: defensive — with no published group result the statically applied config maps stay
+    // authoritative.
     if(!group_result)
         return;