fix(models): H3's image-to-video latent had nowhere to wire

Studio's latent port does not exist in this family, so the node could be added,
filled in and never connected. Its LATENT and keyframe CONDITIONING now reach the
sampler, with a test that every open core input stays reachable in both families.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

movie_editor/backend/pipeline_wiring.py

@@ -121,7 +121,13 @@ FAMILY_WIRING: dict[str, dict] = {
                              ("CONDITIONING", None, _H3_KEYFRAME_PORT)],
             "video_latent": [("LATENT", None, _H3_LATENT_PORT),
                              ("CONDITIONING", None, _H3_KEYFRAME_PORT)],
-            "image_processing": [("IMAGE", None, "FunPackStudio.source_image")],
+            # An H3 Image to Video node is an image_processing node that also emits the AV
+            # latent and its keyframe pins. Without these two the LATENT output had nowhere
+            # to go at all: Studio's latent port does not exist in this family, so the node
+            # could be added and never wired into anything.
+            "image_processing": [("IMAGE", None, "FunPackStudio.source_image"),
+                                 ("LATENT", None, _H3_LATENT_PORT),
+                                 ("CONDITIONING", None, _H3_KEYFRAME_PORT)],
         },
         "type_chain_terminals": {"LATENT": [_H3_LATENT_PORT],
                                  "CONDITIONING": [_H3_KEYFRAME_PORT]},

movie_editor/tests/test_pipeline_wiring.py

@@ -467,3 +467,39 @@ def test_a_pipeline_the_user_edited_is_never_rebuilt_under_them():
     models["model_family"] = "minimax_h3"
     assert pipeline_wiring.reseed_for_family(models, OI_FILES) is False
     assert any(s["id"] == "mine" for s in models["slots"])
+
+
+# ── every output a role can emit has somewhere to go ──────────────────────────
+
+def test_an_h3_image_to_video_node_can_wire_all_three_of_its_outputs():
+    """It is an image node that also emits the AV latent and its keyframe pins. Studio's
+    latent port does not exist in this family, so without these the LATENT output could be
+    added to the pipeline and never wired into anything."""
+    targets = pipeline_wiring._role_targets("minimax_h3")["image_processing"]
+    by_type = {t: p for t, _n, p in targets}
+    assert by_type["IMAGE"] == "FunPackStudio.source_image"
+    assert by_type["LATENT"] == "FunPackLTXAVSceneChainSampler.latent_template"
+    assert by_type["CONDITIONING"] == "FunPackLTXAVSceneChainSampler.h3_keyframes"
+
+
+def test_every_latent_role_reaches_a_port_in_every_family():
+    """A role whose output type has no destination is a node the user can add, fill in and
+    never connect — with nothing saying why."""
+    for family in ("ltxav", "minimax_h3"):
+        targets = pipeline_wiring._role_targets(family)
+        for role in ("empty_latent", "video_latent", "image_processing"):
+            assert any(t == "LATENT" for t, _n, _p in targets.get(role, [])), (family, role)
+
+
+def test_every_open_core_input_is_reachable_from_some_role():
+    """The ports the builder leaves for user loaders must all be offered somewhere, or an
+    input exists that nothing in the panel can ever feed."""
+    for family in ("ltxav", "minimax_h3"):
+        offered = {p for rules in pipeline_wiring._role_targets(family).values()
+                   for _t, _n, p in rules}
+        offered |= {p for ports in pipeline_wiring._chain_terminals(family).values()
+                    for p in ports}
+        for port in pipeline_wiring._open_core(family):
+            if port in pipeline_wiring._hidden_ports(family):
+                continue
+            assert port in offered, (family, port)