feat(imaging): add pure-Rust Skia backend (#112)

tools/ci-matrix/src/api_surface.rs

@@ -932,6 +932,16 @@ fn validate_features(name: &str, actual: &BTreeMap<String, Vec<String>>) -> Resu
         ]),
         "libremetaverse-imaging-skia" => BTreeMap::from([
             ("default".to_owned(), Vec::new()),
+            (
+                "rust-skia".to_owned(),
+                vec![
+                    "dep:image-webp".to_owned(),
+                    "dep:skia-rs-codec".to_owned(),
+                    "skia-rs-codec/gif".to_owned(),
+                    "skia-rs-codec/jpeg".to_owned(),
+                    "skia-rs-codec/png".to_owned(),
+                ],
+            ),
             ("skia".to_owned(), vec!["dep:skia-safe".to_owned()]),
         ]),
         "libremetaverse-voice-webrtc" => BTreeMap::from([
@@ -1232,7 +1242,7 @@ The exact mapping, exported-marker, feature, and normalized Rust declaration has
 - .NET events become `subscribe_*` calls returning an owned `Subscription`; callbacks are `Send + Sync` and dispatch outside internal locks.\n\
 - `IDisposable` becomes explicit idempotent shutdown plus `Drop`; cancellation remains a typed `Error::Cancelled`.\n\
 - Closed C# enums retain fixed discriminants and are SemVer-breaking to extend; flags retain unknown bits, while public Rust error enums are `non_exhaustive`.\n\
-- Optional native backends remain feature-gated (`jpeg2000`, `skia`, `vorbis`, `real-audio`); default and empty-default sets are part of the baseline.\n\
+- Optional native and pure-Rust backends remain feature-gated (`jpeg2000`, `rust-j2k`, `skia`, `rust-skia`, `vorbis`, `real-audio`); default and empty-default sets are part of the baseline.\n\
 - Capability HTTP injection uses project-owned `HttpMessageHandler`, `CapsHttpLimits`, and `with_native_transport`; the internal `reqwest` client is not part of the public surface.\n\
 - External C# signature types map to core/std, adopted cross-platform crates, or project-owned boundary types; no third-party crate path leaks through mapped signatures or public Rust declarations.\n\n\
 ## Compile consumers\n\n\

tools/ci-matrix/src/lib.rs

@@ -38,7 +38,7 @@ const REQUIRED_PROFILES: [&str; 7] = [
     "windows-stable-portable",
     "macos-stable-portable",
 ];
-const REQUIRED_FEATURE_SETS: [&str; 12] = [
+const REQUIRED_FEATURE_SETS: [&str; 13] = [
     "all-features",
     "dds-bc67",
     "default",
@@ -48,11 +48,12 @@ const REQUIRED_FEATURE_SETS: [&str; 12] = [
     "no-default-features",
     "real-audio",
     "rust-j2k",
+    "rust-skia",
     "skia",
     "tests",
     "vorbis",
 ];
-const REQUIRED_FEATURES: [(&str, &str); 8] = [
+const REQUIRED_FEATURES: [(&str, &str); 9] = [
     ("libremetaverse", "dds-bc67"),
     ("libremetaverse", "jpeg2000"),
     ("libremetaverse", "rust-j2k"),
@@ -60,6 +61,7 @@ const REQUIRED_FEATURES: [(&str, &str); 8] = [
     ("libremetaverse-imaging", "jpeg2000"),
     ("libremetaverse-imaging", "rust-j2k"),
     ("libremetaverse-imaging-skia", "skia"),
+    ("libremetaverse-imaging-skia", "rust-skia"),
     ("libremetaverse-voice-webrtc", "real-audio"),
 ];