feat(smargon): ground SCS limits + host guidance from MX-lab reference client

resources_2/Smargon.py (the MX-lab SmarGonController) gives real per-axis SCS
limits and the server hostname convention. Update smargon.yaml:
- SHX/SHY [-2,2], SHZ [10,22] (home ~18, not centred on 0), CHI [0,65],
  PHI [-180,180]  (was placeholder [-2.5,2.5] for the SH axes; SHZ was wrong).
- host: note it must be the actual reachable server (ref used mxlab1-smargopolo).
- Note PHI is continuous and the reference client wraps to [-180,180) before
  sending -- flagged as an open design question, not yet handled here.

Still DRAFT / untested against hardware.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

csaxs_bec/device_configs/smargon.yaml

@@ -9,7 +9,9 @@ smargon:
   description: SmarGon goniometer (SCS axes via smargopolo REST API)
   deviceClass: csaxs_bec.devices.smargon.smargon.SmarGon
   deviceConfig:
-    host: smargopolo          # smargopolo server hostname
+    host: smargopolo          # smargopolo server hostname -- SET TO THE ACTUAL SERVER
+                              # (the MX-lab reference client used "mxlab1-smargopolo";
+                              #  use the hostname reachable from the beamline network)
     port: 3000                # REST API port
     timeout: 5.0              # per-request transport timeout [s]
     has_omega: false          # set true on builds with the OMEGA rotation drive
@@ -27,10 +29,17 @@ smargon:
     # PUT is rejected, or -- if the fault only shows after partial motion -- the
     # device aborts the move on the controller's ERROR mode). Omit an axis here to
     # leave it unbounded in BEC and rely on the controller.
+    #
+    # Values below are taken from the MX-lab reference client (resources_2/Smargon.py)
+    # -- a good grounded starting point, but VERIFY against this build. Note SHZ is
+    # NOT centred on 0 (home is SHZ~18), and PHI is a continuous axis the reference
+    # client wraps to [-180, 180) before sending (see the phi-wrap note in the docs).
     limits:
-      SHX: [-2.5, 2.5]
-      SHY: [-2.5, 2.5]
-      SHZ: [-2.5, 2.5]
+      SHX: [-2, 2]
+      SHY: [-2, 2]
+      SHZ: [10, 22]
+      CHI: [0, 65]
+      PHI: [-180, 180]
     poll_interval: 0.1        # readback polling cadence while moving [s]
     move_timeout: 60.0        # per-move timeout [s]
   deviceTags: