feat(ghpython): Cf_InverseKinematics warns on wired-but-None inputs

If `planner` or `target` is wired (SourceCount > 0) but the upstream
returned None, surface a warning naming the input — typically means
the upstream component itself failed (e.g. AnalyticalKinematicsPlanner
returning None when its solver doesn't accept the loaded cell). The
old silent `return None` made it hard to tell whether IK was broken
or simply not given a usable input.

Unwired inputs stay silent so the canvas isn't noisy while the user
is still building it.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: gonzalocasas

src/compas_fab/ghpython/components_cpython/Cf_InverseKinematics/code.py

@@ -40,7 +40,15 @@
 
 class InverseKinematicsComponent(Grasshopper.Kernel.GH_ScriptInstance):
     def RunScript(self, planner, target, start_state, group: str):
-        if not (planner and target):
+        if planner is None or target is None:
+            # Warn only when the input *is* wired but the upstream returned
+            # None (i.e. upstream silently failed). If nothing is wired, the
+            # user is still building the canvas — staying quiet keeps it clean.
+            for name, value in (("planner", planner), ("target", target)):
+                if value is None:
+                    param = next(p for p in ghenv.Component.Params.Input if p.Name == name)  # noqa: F821
+                    if param.SourceCount > 0:
+                        warning(ghenv.Component, "{} input is wired but received None; check the upstream component for errors.".format(name))  # noqa: F821
             return None
 
         if not isinstance(target, Target):