fix(media-proxy): clamp the webp effort override to the encoder maximum (#1834)

fluxer_media_proxy/src/media_process.rs

@@ -14,6 +14,7 @@ use thiserror::Error;
 const ANIMATED_ENCODE_FLUSH_HEADROOM_MS: i64 = 3_000;
 const PNG_SIGNATURE: &[u8; 8] = b"\x89PNG\r\n\x1a\n";
 const APNG_FRAME_PNG_SUFFIX: &str = ".png[strip,compression=9,filter=all]";
+const VIPS_WEBP_MAX_EFFORT: u8 = 6;
 static PNG_CRC_TABLE: OnceLock<[u32; 256]> = OnceLock::new();
 
 #[derive(Clone, Debug)]
@@ -188,7 +189,7 @@ fn output_suffix(
         "false"
     };
     let effort = effort_override
-        .map(|v| v.min(9))
+        .map(|v| v.min(VIPS_WEBP_MAX_EFFORT))
         .unwrap_or_else(|| effort_for(quality, animated));
     let suffix = match format {
         AssetExtension::Jpeg => format!(".jpg[Q={q},strip,interlace=true,optimize_coding=true]"),
@@ -2242,6 +2243,22 @@ mod tests {
         delays
     }
 
+    #[test]
+    fn webp_effort_override_is_clamped_to_the_encoder_maximum() {
+        for requested in [7u8, 8, 9, 200] {
+            let suffix =
+                output_suffix(AssetExtension::Webp, "high", None, Some(requested)).unwrap();
+            let suffix = suffix.to_str().unwrap().to_owned();
+            assert!(
+                suffix.contains("effort=6"),
+                "effort={requested} produced {suffix}, but libvips webpsave rejects effort above 6 \
+                 and silently falls back to its own default"
+            );
+        }
+        let suffix = output_suffix(AssetExtension::Webp, "high", None, Some(5)).unwrap();
+        assert!(suffix.to_str().unwrap().contains("effort=5"));
+    }
+
     #[test]
     fn animated_webp_default_effort_matches_fast_tier() {
         assert_eq!(2, effort_for("low", true));