Let a tower choose its camera's auto-exposure target: --target

The Alvium recipe sets no IntensityControllerTarget, so a camera kept its
default of 50 %, which burns out the sky over a dark forest; staeffelsberg's
colour camera runs at 20 (set by hand in the Viewer), rietschen's Manta at
30. export_camera_profile.py --target <percent> now sets it for either
family (IntensityControllerTarget, or ExposureAutoTarget on a Manta). Without
the option nothing changes. For podrosche, whose migration plans 20 %.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/tower-installation.md

@@ -696,6 +696,11 @@ property the Viewer workflow exists to provide: GenICam validity is stateful, so
 a hand-written XML can be individually plausible and collectively wrong. Here
 the camera is the judge, and anything it refused is printed rather than assumed.
 
+`--target <percent>` sets the auto-exposure target, a tower's own choice: the
+Alvium recipe sets none, so the camera keeps its default of 50, which burns out
+the sky over a dark forest. Staeffelsberg runs at 20, rietschen at 30. The keep
+rule reads the target back from the camera, so nothing else has to change.
+
 Read the summary line it prints - it is the number that decides whether the
 profile can be delivered at all:
 

scripts/export_camera_profile.py

@@ -193,6 +193,20 @@ def has_feature(cam, name):
         return False
 
 
+def with_target(recipe, family, target):
+    """The recipe with its auto-exposure target set to `target` percent.
+
+    A tower's own choice, not a recipe's: staeffelsberg's colour camera runs at
+    20 %, rietschen's at 30, where the Alvium's default of 50 burnt out the sky.
+    The keep rule reads the target back from the camera, so nothing else needs
+    to know. An existing target entry is replaced; otherwise it goes last."""
+    if target is None:
+        return recipe
+    name = "ExposureAutoTarget" if family == "gige" else "IntensityControllerTarget"
+    out = [(n, v) for n, v in recipe if n != name]
+    return out + [(name, float(target))]
+
+
 def recipe_family(cam):
     """'gige' for a camera that only knows the older names, else 'alvium'."""
     if not has_feature(cam, "ExposureTime") and has_feature(cam, "ExposureTimeAbs"):
@@ -270,6 +284,9 @@ def main():
     ap.add_argument("--camera", default=None, help="camera id (default: the first real one)")
     ap.add_argument("--family", default="auto", choices=("auto", "alvium", "gige"),
                     help="which recipe set (default: from the features the camera has)")
+    ap.add_argument("--target", type=float, default=None,
+                    help="auto-exposure target in percent (default: the recipe's, or the "
+                         "camera's own where the recipe sets none)")
     ap.add_argument("--dry-run", action="store_true")
     args = ap.parse_args()
 
@@ -294,7 +311,8 @@ def main():
 
         with cam:
             family = recipe_family(cam) if args.family == "auto" else args.family
-            recipe = (GIGE_RECIPES if family == "gige" else RECIPES)[args.profile]
+            recipe = with_target((GIGE_RECIPES if family == "gige" else RECIPES)[args.profile],
+                                 family, args.target)
             print(f"camera  : {cam.get_id()}  {cam.get_model()}")
             print(f"profile : {args.profile} ({family} recipe){'  (dry run)' if args.dry_run else ''}")
             refused = []