Wire progressive JPEG, AVIF speed, and custom per-format quality to encoder

- Add EncoderOptions struct with progressive_jpeg and avif_speed fields
- Pass encoder options through ProcessingJob to PipelineExecutor
- mozjpeg set_progressive_mode() called when progressive JPEG enabled
- AVIF encoder speed now configurable (was hardcoded to 6)
- run_processing uses CompressConfig::Custom when user overrides preset defaults
- Executor properly handles AVIF quality and PNG level in Custom mode

pixstrip-core/src/encoder.rs

@@ -4,11 +4,28 @@ use std::path::Path;
 use crate::error::{PixstripError, Result};
 use crate::types::{ImageFormat, QualityPreset};
 
-pub struct OutputEncoder;
+#[derive(Debug, Clone, Default)]
+pub struct EncoderOptions {
+    pub progressive_jpeg: bool,
+    pub avif_speed: u8,
+}
+
+pub struct OutputEncoder {
+    pub options: EncoderOptions,
+}
 
 impl OutputEncoder {
     pub fn new() -> Self {
-        Self
+        Self {
+            options: EncoderOptions {
+                progressive_jpeg: false,
+                avif_speed: 6,
+            },
+        }
+    }
+
+    pub fn with_options(options: EncoderOptions) -> Self {
+        Self { options }
     }
 
     pub fn encode(
@@ -60,6 +77,9 @@ impl OutputEncoder {
         let mut comp = mozjpeg::Compress::new(mozjpeg::ColorSpace::JCS_RGB);
         comp.set_size(width, height);
         comp.set_quality(quality as f32);
+        if self.options.progressive_jpeg {
+            comp.set_progressive_mode();
+        }
 
         let mut output = Vec::new();
         let mut started = comp.start_compress(&mut output).map_err(|e| PixstripError::Processing {
@@ -121,9 +141,10 @@ impl OutputEncoder {
         let mut buf = Vec::new();
         let cursor = Cursor::new(&mut buf);
         let rgba = img.to_rgba8();
+        let speed = self.options.avif_speed.clamp(1, 10);
         let encoder = image::codecs::avif::AvifEncoder::new_with_speed_quality(
             cursor,
-            6,
+            speed,
             quality,
         );
         image::ImageEncoder::write_image(