feat(bec_widgets): add at_each_angle hook dropdown to TomoParamsWidget

A new "At-each-angle hook" combo box in the params panel, built from
the live tomo_at_each_angle_hooks global var (no hardcoded mirror of
registered names). Rebuilt on every populate (i.e. every 2s poll while
not editing, and on entering edit mode), so hooks registered/
unregistered from the CLI while the dialog is open show up
automatically. The currently-set hook is always shown even if it
isn't in the published list (e.g. registered in a different or
since-restarted session), labeled accordingly, so it's never silently
hidden. Special-cased in _populate_fields()/_read_fields() like
tomo_type -- the generic QComboBox handling assumes integer data,
which doesn't fit a hook name string or None. This also makes the
manual params["at_each_angle_hook"] pass-through in
add_edited_to_queue() (added when there was no widget for this field)
redundant; removed, since _read_fields() now supplies it directly
from the dropdown.

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

csaxs_bec/bec_widgets/widgets/tomo_params/tomo_params.py

@@ -386,6 +386,16 @@ class TomoParamsWidget(BECWidget, QWidget):
             max_=10.0,
             decimals=3,
         )
+        self._pw["at_each_angle_hook"] = QComboBox()
+        self._pw["at_each_angle_hook"].setEnabled(False)
+        self._pw["at_each_angle_hook"].setToolTip(
+            "Run a registered custom function at every projection angle instead "
+            "of the normal acquisition (e.g. move a polarizer in/out between "
+            "exposures). Registered from the CLI with "
+            "flomni.register_at_each_angle_hook(name, func) -- this list refreshes "
+            "automatically while the dialog is open."
+        )
+        common_form.addRow("At-each-angle hook:", self._pw["at_each_angle_hook"])
         vbox.addLayout(common_form)
 
         # type-1 section
@@ -523,8 +533,10 @@ class TomoParamsWidget(BECWidget, QWidget):
             self._pw["tomo_type"].setCurrentIndex(idx)
             self._pw["tomo_type"].blockSignals(False)
 
+        self._populate_at_each_angle_hook_combo(params.get("at_each_angle_hook"))
+
         for key, widget in self._pw.items():
-            if key in ("tomo_type", "_requested_total"):
+            if key in ("tomo_type", "_requested_total", "at_each_angle_hook"):
                 continue
             val = params.get(key)
             if val is None:
@@ -562,14 +574,39 @@ class TomoParamsWidget(BECWidget, QWidget):
 
         self._update_type_visibility(type_val)
 
+    def _populate_at_each_angle_hook_combo(self, current: Optional[str]) -> None:
+        """Rebuild the at_each_angle_hook dropdown from the live
+        ``tomo_at_each_angle_hooks`` registry (published by
+        ``Flomni.register_/unregister_at_each_angle_hook()``) and select
+        ``current``.
+
+        ``current`` is added as its own entry even if it isn't in the
+        published list -- e.g. it was registered in a different, or a
+        since-restarted, session -- so the operator sees what's actually
+        set instead of it silently disappearing from the dropdown.
+        """
+        combo = self._pw["at_each_angle_hook"]
+        registered = self._gv_get("tomo_at_each_angle_hooks") or []
+        combo.blockSignals(True)
+        combo.clear()
+        combo.addItem("None (default)", None)
+        for name in registered:
+            combo.addItem(name, name)
+        if current and current not in registered:
+            combo.addItem(f"{current}  (not registered in this session)", current)
+        idx = combo.findData(current)
+        combo.setCurrentIndex(idx if idx >= 0 else 0)
+        combo.blockSignals(False)
+
     def _read_fields(self) -> dict[str, Any]:
         """Read all input widgets into a params dict."""
         params: dict[str, Any] = {}
 
         params["tomo_type"] = self._pw["tomo_type"].currentData()
+        params["at_each_angle_hook"] = self._pw["at_each_angle_hook"].currentData()
 
         for key, widget in self._pw.items():
-            if key in ("tomo_type", "_requested_total"):
+            if key in ("tomo_type", "_requested_total", "at_each_angle_hook"):
                 continue
             if isinstance(widget, QDoubleSpinBox):
                 params[key] = widget.value()
@@ -933,13 +970,6 @@ class TomoParamsWidget(BECWidget, QWidget):
         would silently ignore an in-progress edit.
         """
         params = self._read_fields()
-        # _read_fields() only covers widget-backed params (self._pw); there's
-        # no editable widget for at_each_angle_hook yet, so it would
-        # otherwise be silently absent from this job's params -- which would
-        # make the executor leave whatever hook the *previous* queued job
-        # left active in place for this one too. Pass the current live value
-        # through unchanged instead of dropping it.
-        params["at_each_angle_hook"] = self._gv_get("at_each_angle_hook")
         error = self._validate(params)
         if error:
             QMessageBox.warning(self, "Validation error", error)