Merge branch 'main' into feat/plugin-feature

Resolve five conflicts, all of which needed both sides rather than a pick:

- BackgroundSlicingProcess: ours was a pure tabs->spaces reformat of base, so
  keep main's per-filament volume/nozzle map read-back (its only change here).
- GUI_App: main's #12506 else-if attached to an `if` this branch deleted;
  re-expressed onto the same-agent early-return path (the agent factory caches
  per id, so pointer equality is the same predicate).
- MainFrame: both sides relocated Sync Presets independently; keep main's
  push_notification plus the branch's Plugins menu items.
- Tab: the "TODO: Orca: Support hybrid" blocks were unchanged base, not a branch
  decision; take main's enabled Hybrid to match the already auto-merged siblings.
- test_config: union of both sides' cases (6 plugin + 9 multi-nozzle).

CMakeLists.txt

@@ -835,7 +835,7 @@ endif ()
 set(L10N_DIR "${SLIC3R_RESOURCES_DIR}/i18n")
 set(BBL_L18N_DIR "${CMAKE_CURRENT_SOURCE_DIR}/localization/i18n")
 add_custom_target(gettext_make_pot
-    COMMAND xgettext --keyword=L --keyword=_L --keyword=_u8L --keyword=L_CONTEXT:1,2c --keyword=_L_PLURAL:1,2 --add-comments=TRN --from-code=UTF-8 --no-location --debug --boost
+    COMMAND xgettext --keyword=L --keyword=_L --keyword=_u8L --keyword=L_CONTEXT:1,2c --keyword=_CTX:1,2c --keyword=_CTX_utf8:1,2c --keyword=_L_PLURAL:1,2 --add-comments=TRN --from-code=UTF-8 --no-location --debug --boost
         -f "${BBL_L18N_DIR}/list.txt"
         -o "${BBL_L18N_DIR}/OrcaSlicer.pot"
     COMMAND hintsToPot ${SLIC3R_RESOURCES_DIR} ${BBL_L18N_DIR}