fix: declare env dependencies and map selector duration to frames

- Add env:VOLC_ACCESSKEY and env:VOLC_SECRETKEY to dependencies
- Map selector 'duration' (seconds) to Jimeng 'frames' (121/241)
- Add 4 selector duration mapping regression tests
- 59 tests pass

Fixes calesthio's third review feedback on PR #341.

tests/contracts/test_jimeng_video.py

@@ -378,3 +378,26 @@ class TestSchemaValidation:
         schema = JimengVideo().input_schema
         for valid in [0, 1, 42, 999999]:
             jsonschema.validate({"prompt": "test", "seed": valid}, schema)
+
+
+# ------------------------------------------------------------------
+# Selector duration → frames mapping
+# ------------------------------------------------------------------
+
+class TestSelectorDurationMapping:
+
+    def test_duration_5_maps_to_121_frames(self):
+        payload = JimengVideo._build_payload({"prompt": "x", "duration": 5})
+        assert payload["frames"] == 121
+
+    def test_duration_10_maps_to_241_frames(self):
+        payload = JimengVideo._build_payload({"prompt": "x", "duration": 10})
+        assert payload["frames"] == 241
+
+    def test_duration_defaults_to_5_when_absent(self):
+        payload = JimengVideo._build_payload({"prompt": "x"})
+        assert payload["frames"] == 121
+
+    def test_frames_takes_priority_over_duration(self):
+        payload = JimengVideo._build_payload({"prompt": "x", "frames": 241, "duration": 5})
+        assert payload["frames"] == 241

tools/video/jimeng_video.py

@@ -57,7 +57,7 @@ class JimengVideo(BaseTool):
     determinism = Determinism.STOCHASTIC
     runtime = ToolRuntime.API
 
-    dependencies = []
+    dependencies = ["env:VOLC_ACCESSKEY", "env:VOLC_SECRETKEY"]
     install_instructions = (
         "Set VOLC_ACCESSKEY and VOLC_SECRETKEY to your Volcengine IAM credentials.\n"
         "  Get them at https://console.volcengine.com/iam/keymanage\n"
@@ -252,13 +252,22 @@ class JimengVideo(BaseTool):
             model=_REQ_KEY_VIDEO,
         )
 
+    @staticmethod
+    def _duration_to_frames(duration: int) -> int:
+        if duration >= 10:
+            return 241
+        return 121
+
     @staticmethod
     def _build_payload(inputs: dict[str, Any]) -> dict[str, Any]:
         operation = inputs.get("operation", "text_to_video")
+        frames = inputs.get("frames")
+        if frames is None:
+            frames = JimengVideo._duration_to_frames(int(inputs.get("duration", 5)))
         payload: dict[str, Any] = {
             "req_key": _REQ_KEY_VIDEO,
             "prompt": inputs["prompt"],
-            "frames": int(inputs.get("frames", 121)),
+            "frames": int(frames),
             "aspect_ratio": inputs.get("aspect_ratio", "16:9"),
             "seed": int(inputs.get("seed", -1)),
         }