fix(flomni): always define tomo_alignment_fit

The global var was deleted on stage-in / new alignment and never created
at startup, so manual tweaks like fit[0][2] += 5.0 failed with an
undefined variable. reset_tomo_alignment_fit() now writes an all-zero
2x5 fit instead of deleting, and Flomni.__init__ creates it if missing
(an existing fit is kept so it survives client restarts).

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

csaxs_bec/bec_ipython_client/plugins/flomni/flomni.py

@@ -1406,7 +1406,21 @@ class FlomniAlignmentMixin:
                 logger.warning("Not applying any correction.")
 
     def reset_tomo_alignment_fit(self):
-        self.client.delete_global_var("tomo_alignment_fit")
+        """Reset the alignment fit to all zeros (no offset applied).
+
+        Writes zeros rather than deleting the global var, so that
+        "tomo_alignment_fit" is always defined and can be tweaked by hand
+        (see the layout comment above get_alignment_offset).
+        """
+        self.client.set_global_var("tomo_alignment_fit", np.zeros((2, 5)).tolist())
+
+    def ensure_tomo_alignment_fit(self):
+        """Define "tomo_alignment_fit" (all zeros) if it does not exist yet.
+
+        An existing fit is left untouched so it survives a client restart.
+        """
+        if self.client.get_global_var("tomo_alignment_fit") is None:
+            self.reset_tomo_alignment_fit()
 
     def read_alignment_offset(
         self,
@@ -1810,6 +1824,7 @@ class Flomni(
         self.label_printer = PTouchLabelPrinter(host="BRN94DDF8AAB8EC.psi.ch", template_number=1)
         self.set_client(client)
 
+        self.ensure_tomo_alignment_fit()
         self._maybe_reset_params_on_account_change()
 
     def set_web_password(self, password: str) -> None: