feat(machine): add SLS injection/top-up status PV

Registers AGETI-CVME-MASTER-TMA:SR-Inj-Status-I (the injection-system
enum PV) as injection_status, alongside the other machine-status PVs
(curr, ofb, shutter). readoutPriority is 'monitored', matching curr,
so the value is captured continuously throughout each scan rather
than only once at scan start -- a top-up can start or stop mid-scan.

'0' / 'Filling Storage Ring' means the ring is being refilled.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0132KBoxsovfcMNRGJhS1Pbw

csaxs_bec/device_configs/machine.yml

@@ -51,3 +51,22 @@ operator:
   softwareTrigger: false
   deviceTags:
     - machine
+
+injection_status:
+  # Top-up gating: '0' / 'Filling Storage Ring' means the storage ring is
+  # being refilled. readoutPriority is 'monitored' (not 'baseline') so this
+  # is captured continuously throughout the scan, not just read once at
+  # scan start - a top-up can start or stop mid-scan.
+  description: SLS injection/top-up status
+  deviceClass: ophyd_devices.EpicsSignalRO
+  deviceConfig:
+    read_pv: AGETI-CVME-MASTER-TMA:SR-Inj-Status-I
+    auto_monitor: true
+    string: true
+  onFailure: buffer
+  enabled: true
+  readoutPriority: monitored
+  readOnly: true
+  softwareTrigger: false
+  deviceTags:
+    - machine