feat(flomni): fire the single-point acquisition warning on the off->on transition

Previously the tomo_acquire_at_angle()-vs-tomo_scan_projection()
reminder only printed when tomo_parameters() happened to be called
afterward -- easy to miss if you just flip
single_point_instead_of_fermat_scan directly. Its setter now prints
the same note immediately when the value transitions False->True.
Gated on the transition (checked via the property's own getter before
the write) so restoring an already-True value across consecutive
queued jobs doesn't reprint it every time -- sim-verified: silent on
False->False, True->True (repeat), and True->False; prints exactly
once per False->True flip.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

csaxs_bec/bec_ipython_client/plugins/flomni/flomni.py

@@ -2184,6 +2184,18 @@ class Flomni(
 
     @single_point_instead_of_fermat_scan.setter
     def single_point_instead_of_fermat_scan(self, val: bool):
+        # Fire the reminder right at the moment it's switched on, not just
+        # when tomo_parameters() happens to be called afterward. Gated on
+        # the off->on transition (reading the property itself for the old
+        # value, before the write below) so restoring the same True value
+        # across consecutive queued jobs doesn't reprint it every time.
+        if val and not self.single_point_instead_of_fermat_scan:
+            print(
+                "\x1b[93mNote: with single-point mode on, acquire a single projection "
+                "(including inside a custom at_each_angle hook) with "
+                "tomo_acquire_at_angle(angle), not tomo_scan_projection(angle) -- the "
+                "latter always runs a full Fermat scan regardless of this setting.\x1b[0m"
+            )
         self.client.set_global_var("single_point_instead_of_fermat_scan", val)
 
     @property