fix(docker): Pin Rust nightly for WASM build compatibility

Rust 1.93+ removed -Zbuild-std support for wasm32-unknown-emscripten.
Pin to nightly-2026-01-20 which still supports this feature, required
for building cdylib crate type for Godot WASM exports.

Author: snowfrogdev

docker/Dockerfile

@@ -26,9 +26,13 @@ ENV EMSDK=/opt/emsdk
 ENV PATH="${EMSDK}:${EMSDK}/upstream/emscripten:${PATH}"
 
 # Rust nightly toolchain with targets
-RUN rustup toolchain install nightly \
-    && rustup target add x86_64-pc-windows-gnu --toolchain nightly \
-    && rustup component add rust-src --toolchain nightly
+# Pin to nightly-2026-01-20 to avoid breaking change in Rust 1.93+ where
+# -Zbuild-std is no longer supported with wasm32-unknown-emscripten target
+ENV RUST_NIGHTLY=nightly-2026-01-20
+RUN rustup toolchain install $RUST_NIGHTLY \
+    && rustup target add x86_64-pc-windows-gnu --toolchain $RUST_NIGHTLY \
+    && rustup component add rust-src --toolchain $RUST_NIGHTLY \
+    && rustup default $RUST_NIGHTLY
 
 # Copy entrypoint script
 COPY build.sh /usr/local/bin/build

docker/build.sh

@@ -55,7 +55,7 @@ fi
 
 case "$TARGET" in
     windows)
-        cargo +nightly build --manifest-path bindings/godot/Cargo.toml \
+        cargo build --manifest-path bindings/godot/Cargo.toml \
             --target-dir target --target x86_64-pc-windows-gnu $FEATURES $CARGO_PROFILE_FLAG
         cp target/x86_64-pc-windows-gnu/$PROFILE/bobbin_godot.dll "$BIN_DIR/bobbin_godot$SUFFIX.dll"
         ;;
@@ -66,9 +66,9 @@ case "$TARGET" in
         # Set rustflags for WASM target (side module for Godot)
         export CARGO_TARGET_WASM32_UNKNOWN_EMSCRIPTEN_RUSTFLAGS="-C link-args=-pthread -C target-feature=+atomics -C link-args=-sSIDE_MODULE=2 -C panic=abort -Zlink-native-libraries=no -Cllvm-args=-enable-emscripten-cxx-exceptions=0"
         # Use 'wasm' profile (size-optimized, no LTO)
-        # Note: -Zbuild-std is no longer supported with wasm32-unknown-emscripten target
-        cargo +nightly build --manifest-path bindings/godot/Cargo.toml \
-            --target-dir target --profile wasm --target wasm32-unknown-emscripten
+        # Note: Requires pinned nightly (see Dockerfile) - newer nightlies removed -Zbuild-std support for emscripten
+        cargo build --manifest-path bindings/godot/Cargo.toml \
+            -Zbuild-std=std,panic_abort --target-dir target --profile wasm --target wasm32-unknown-emscripten
         # Run wasm-opt for aggressive size optimization (more efficient than LTO for WASM)
         WASM_FILE="target/wasm32-unknown-emscripten/wasm/bobbin_godot.wasm"
         WASM_OPT="$EMSDK/upstream/bin/wasm-opt"
@@ -80,7 +80,7 @@ case "$TARGET" in
         cp "$WASM_FILE" "$BIN_DIR/bobbin_godot.wasm"
         ;;
     linux)
-        cargo +nightly build --manifest-path bindings/godot/Cargo.toml --target-dir target $FEATURES $CARGO_PROFILE_FLAG
+        cargo build --manifest-path bindings/godot/Cargo.toml --target-dir target $FEATURES $CARGO_PROFILE_FLAG
         cp target/$PROFILE/libbobbin_godot.so "$BIN_DIR/libbobbin_godot$SUFFIX.so"
         ;;
     all)