Add CP load mode to 2D sweep and supply sanity checks

- 2D sweep now supports CC (constant current) and CP (constant power)
  load modes via --load-mode flag (CLI) and combobox (GUI)
- Supply capability check before all sweeps: validates max voltage
  against supply range and prints V/I/P summary
- Renamed sweep-vi args from --i-start/stop/step to --l-start/stop/step
  to reflect that the load setpoint can be current or power
- GUI labels update dynamically based on selected load mode

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

testbench/cli.py

@@ -439,10 +439,12 @@ def cmd_efficiency(bench: MPPTTestbench, args: argparse.Namespace) -> None:
 
 
 def cmd_sweep_vi(bench: MPPTTestbench, args: argparse.Namespace) -> None:
-    """Run a 2D voltage × load current sweep."""
+    """Run a 2D voltage × load sweep."""
+    mode = args.load_mode
+    unit = "A" if mode == "CC" else "W"
     print(
         f"2D sweep: V={args.v_start:.1f}-{args.v_stop:.1f}V (step {args.v_step:.1f}), "
-        f"I_load={args.i_start:.2f}-{args.i_stop:.2f}A (step {args.i_step:.2f}), "
+        f"{mode}={args.l_start:.2f}-{args.l_stop:.2f}{unit} (step {args.l_step:.2f}), "
         f"I_limit={args.current_limit:.1f}A, settle={args.settle:.1f}s"
     )
     print()
@@ -451,11 +453,12 @@ def cmd_sweep_vi(bench: MPPTTestbench, args: argparse.Namespace) -> None:
         v_start=args.v_start,
         v_stop=args.v_stop,
         v_step=args.v_step,
-        i_start=args.i_start,
-        i_stop=args.i_stop,
-        i_step=args.i_step,
+        l_start=args.l_start,
+        l_stop=args.l_stop,
+        l_step=args.l_step,
         current_limit=args.current_limit,
         settle_time=args.settle,
+        load_mode=mode,
     )
 
     _write_sweep_csv(results, args.output)
@@ -564,7 +567,8 @@ examples:
   %(prog)s sweep --v-start 10 --v-stop 50 --v-step 1 --current-limit 10 -o sweep.csv
   %(prog)s sweep-load --voltage 75 --current-limit 10 --i-start 1 --i-stop 20 --i-step 1 -o load.csv
   %(prog)s efficiency --voltage 36 --current-limit 10 --samples 10
-  %(prog)s sweep-vi --v-start 35 --v-stop 100 --v-step 5 --i-start 0.5 --i-stop 30 --i-step 1 --current-limit 35 -o map.csv
+  %(prog)s sweep-vi --v-start 35 --v-stop 100 --v-step 5 --l-start 0.5 --l-stop 30 --l-step 1 --current-limit 35 -o map.csv
+  %(prog)s sweep-vi --v-start 35 --v-stop 100 --v-step 5 --l-start 50 --l-stop 500 --l-step 50 --load-mode CP --current-limit 35 -o map_cp.csv
   %(prog)s shade-profile --profile cloud_pass.csv --settle 2.0 -o shade_results.csv
   %(prog)s supply set --voltage 24 --current 10
   %(prog)s supply on
@@ -651,13 +655,14 @@ examples:
     p_eff.add_argument("--load-value", type=float)
 
     # sweep-vi (2D)
-    p_svi = sub.add_parser("sweep-vi", help="2D voltage × load current sweep (efficiency map)")
+    p_svi = sub.add_parser("sweep-vi", help="2D voltage × load sweep (efficiency map)")
     p_svi.add_argument("--v-start", type=float, required=True, help="Start voltage (V)")
     p_svi.add_argument("--v-stop", type=float, required=True, help="Stop voltage (V)")
     p_svi.add_argument("--v-step", type=float, required=True, help="Voltage step (V)")
-    p_svi.add_argument("--i-start", type=float, required=True, help="Start load current (A)")
-    p_svi.add_argument("--i-stop", type=float, required=True, help="Stop load current (A)")
-    p_svi.add_argument("--i-step", type=float, required=True, help="Current step (A)")
+    p_svi.add_argument("--l-start", type=float, required=True, help="Start load setpoint (A for CC, W for CP)")
+    p_svi.add_argument("--l-stop", type=float, required=True, help="Stop load setpoint")
+    p_svi.add_argument("--l-step", type=float, required=True, help="Load step size")
+    p_svi.add_argument("--load-mode", choices=["CC", "CP"], default="CC", help="Load mode: CC (current) or CP (power)")
     p_svi.add_argument("--current-limit", type=float, required=True, help="Supply current limit (A)")
     p_svi.add_argument("--settle", type=float, default=2.0, help="Settle time per step (s)")
     p_svi.add_argument("-o", "--output", help="CSV output file")