feat(filters): accept fil_comb(1411) as well as fil_comb(1, 4, 1, 1)

The four-digit code is already the currency of this module: it is what
_all_combinations builds, what fil_trans prints as the selected
combination, and what _fil_trans_report prints for what is currently in
the beam. Requiring commas on the way back in meant reading a code off
the screen and retyping it as four separate arguments.

fil_comb now takes 1411, "1411", (1, 4, 1, 1) or [1, 4, 1, 1], so a
reported combination can be pasted straight back.

A code of the wrong length is rejected with the length it needs rather
than falling through to "expects 4 positions, got 1", which was the
unhelpful error a code would have produced before. bool is excluded from
the integer branch so fil_comb(True) does not quietly become "True".
Digits outside 1..6 are left to the existing per-unit range check, which
names the offending unit.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017kLGTqTyXzTT4swt3CfTkV

csaxs_bec/bec_ipython_client/plugins/cSAXS/filter_transmission.py

@@ -293,31 +293,55 @@ class cSAXSFilterTransmission:
         as the SPEC fil_comb. Use this when a particular filter is wanted; use
         fil_trans when a particular transmission is wanted.
 
+        The four slot numbers may also be given as a single code, which is the
+        form fil_trans prints and _fil_trans_report matches, so a reported
+        combination can be pasted straight back in.
+
         Examples:
             csaxs.fil_comb(1, 4, 1, 1)   # Ti 400 only
-            csaxs.fil_comb(1, 2, 3, 1)   # Si 200 (unit 2) + Si 1600 (unit 3)
-            csaxs.fil_comb(1, 1, 1, 1)   # all out
+            csaxs.fil_comb(1411)         # the same thing
+            csaxs.fil_comb(1, 2, 3, 1)   # Si 234.6 (unit 2) + Si 1661.5 (unit 3)
+            csaxs.fil_comb(1111)         # all out
 
         Safety: identical to fil_trans. Any combination with transmission < 1
         requires DMM through and the CCM active, or an explicit confirmation.
 
         Args:
             *positions: four slot numbers, one per unit, 1..6 (1 = out). A single
-                list or tuple of four is also accepted.
+                list, tuple, or four-digit code such as 1411 is also accepted.
             energy_kev: photon energy. Read from the CCM energy PV if omitted.
             print_only: dry run first and prompt before moving. Defaults to True.
         """
         if not positions:
             print("\nUsage example:")
             print("  csaxs.fil_comb(1, 4, 1, 1)   # one slot number per unit, 1 = out")
+            print("  csaxs.fil_comb(1411)         # or the same as a single code")
             print("  Use csaxs.fil_trans(T) to select by transmission instead.")
             print("\nCurrent filter transmission:")
             self._fil_trans_report(energy_kev=energy_kev)
             return None
 
-        # Accept fil_comb([1, 4, 1, 1]) as well as fil_comb(1, 4, 1, 1)
-        if len(positions) == 1 and isinstance(positions[0], (list, tuple)):
-            positions = tuple(positions[0])
+        # Accept fil_comb(1411) and fil_comb("1411") -- the same four-digit code
+        # that fil_trans prints and _fil_trans_report matches -- as well as
+        # fil_comb(1, 4, 1, 1) and fil_comb([1, 4, 1, 1]).
+        if len(positions) == 1:
+            only = positions[0]
+            if isinstance(only, (list, tuple)):
+                positions = tuple(only)
+            elif isinstance(only, (int, str)) and not isinstance(only, bool):
+                digits = str(only).strip()
+                if not digits.isdigit():
+                    raise ValueError(
+                        f"Cannot read {only!r} as a filter combination. Give one slot "
+                        f"number per unit, e.g. fil_comb(1, 4, 1, 1) or fil_comb(1411)."
+                    )
+                if len(digits) != self._UNITS:
+                    raise ValueError(
+                        f"A filter code has exactly {self._UNITS} digits, one per unit; "
+                        f"got {digits!r}. Slot numbers run 1..{self._PER_UNIT} with 1 = out, "
+                        f"so fil_comb(1411) is unit 2 at position 4 and the rest out."
+                    )
+                positions = tuple(digits)
 
         # --- Energy handling (EPICS only) ---
         if energy_kev is None: