Validate Encoder effort eagerly at construction time

`Encoder::new` now validates effort (must be 1..=10) at construction, matching the existing `decoding_speed` validation, instead of only failing later in call_inner when it maps effort to an `EncoderSpeed`. Error message states the valid range. Added tests covering effort=0/11 (raise ValueError) and effort=10 (succeeds).

Author: nikosavola

src/encode.rs

@@ -100,6 +100,11 @@ impl Encoder {
             }
         };
 
+        let effort = match effort {
+            1..=10 => effort,
+            _ => return Err(PyValueError::new_err("Effort must be between 1 and 10")),
+        };
+
         let use_original_profile = match lossless {
             true => true,
             false => use_original_profile,

test/test_plugin.py

@@ -15,6 +15,21 @@ def test_debug_mode():
     assert exit_code == 0
 
 
+@pytest.mark.parametrize("effort", [0, 11])
+def test_encode_invalid_effort_raises(effort):
+    img = Image.open("test/images/sample.png")
+    temp = tempfile.mktemp(suffix=".jxl")
+    with pytest.raises(ValueError):
+        img.save(temp, effort=effort)
+
+
+def test_encode_boundary_effort_succeeds():
+    img = Image.open("test/images/sample.png")
+    temp = tempfile.mktemp(suffix=".jxl")
+    img.save(temp, effort=10)
+    assert Image.open(temp).size == img.size
+
+
 def test_decode():
     img_jxl = Image.open("test/images/sample.jxl")
     img_png = Image.open("test/images/sample.png")