feat(imaging): default to pure-Rust codecs

tools/check_milestone_06.py

@@ -40,8 +40,8 @@ def check_owned_rust() -> None:
 
 def check_features() -> None:
     imaging = load_toml(OWNED_CRATES[0] / "Cargo.toml")
-    if imaging["features"].get("default") != []:
-        raise SystemExit("imaging default features must stay empty")
+    if imaging["features"].get("default") != ["rust-j2k"]:
+        raise SystemExit("imaging defaults must select only pure-Rust JPEG 2000")
     if imaging["features"].get("jpeg2000") != ["dep:libremetaverse-openjpeg"]:
         raise SystemExit("JPEG 2000 must stay isolated behind its optional feature")
     if imaging["features"].get("rust-j2k") != ["dep:j2k"]:
@@ -50,8 +50,8 @@ def check_features() -> None:
         raise SystemExit("the OpenJPEG adapter dependency must stay optional")
 
     skia = load_toml(OWNED_CRATES[1] / "Cargo.toml")
-    if skia["features"].get("default") != []:
-        raise SystemExit("Skia adapter default features must stay empty")
+    if skia["features"].get("default") != ["rust-skia"]:
+        raise SystemExit("raster adapter defaults must select only pure-Rust codecs")
     if skia["features"].get("skia") != ["dep:skia-safe"]:
         raise SystemExit("Skia must stay isolated behind its optional feature")
     targets = skia.get("target", {}).values()

tools/ci-matrix/src/api_surface.rs

@@ -911,7 +911,10 @@ fn validate_features(name: &str, actual: &BTreeMap<String, Vec<String>>) -> Resu
     let expected = match name {
         "libremetaverse" => BTreeMap::from([
             ("dds-bc67".to_owned(), vec!["dep:bcdec_rs".to_owned()]),
-            ("default".to_owned(), vec!["dds-bc67".to_owned()]),
+            (
+                "default".to_owned(),
+                vec!["dds-bc67".to_owned(), "rust-j2k".to_owned()],
+            ),
             (
                 "jpeg2000".to_owned(),
                 vec!["libremetaverse-imaging/jpeg2000".to_owned()],
@@ -923,7 +926,7 @@ fn validate_features(name: &str, actual: &BTreeMap<String, Vec<String>>) -> Resu
             ("vorbis".to_owned(), vec!["dep:vorbis_rs".to_owned()]),
         ]),
         "libremetaverse-imaging" => BTreeMap::from([
-            ("default".to_owned(), Vec::new()),
+            ("default".to_owned(), vec!["rust-j2k".to_owned()]),
             (
                 "jpeg2000".to_owned(),
                 vec!["dep:libremetaverse-openjpeg".to_owned()],
@@ -931,7 +934,7 @@ fn validate_features(name: &str, actual: &BTreeMap<String, Vec<String>>) -> Resu
             ("rust-j2k".to_owned(), vec!["dep:j2k".to_owned()]),
         ]),
         "libremetaverse-imaging-skia" => BTreeMap::from([
-            ("default".to_owned(), Vec::new()),
+            ("default".to_owned(), vec!["rust-skia".to_owned()]),
             (
                 "rust-skia".to_owned(),
                 vec![
@@ -1242,7 +1245,7 @@ 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 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\
+- Pure-Rust image backends are enabled by default (`rust-j2k`, `rust-skia`); native alternatives remain feature-gated (`jpeg2000`, `skia`, `vorbis`, `real-audio`), and empty-default sets remain 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

@@ -422,7 +422,7 @@ fn audit_cargo_features(root: &Path) -> Result<()> {
     if defaults.iter().any(|feature| {
         matches!(
             feature.as_str(),
-            Some("jpeg2000" | "vorbis" | "dep:vorbis_rs")
+            Some("jpeg2000" | "skia" | "vorbis" | "dep:vorbis_rs")
         )
     }) {
         return Err(MatrixError::new(
@@ -450,6 +450,8 @@ fn audit_cargo_features(root: &Path) -> Result<()> {
     let default_tree = String::from_utf8_lossy(&default_tree.stdout);
     for forbidden in [
         "libremetaverse-openjpeg ",
+        "skia-safe ",
+        "skia-bindings ",
         "vorbis_rs ",
         "ogg_next_sys ",
         "aotuv_lancer_vorbis_sys ",