build: migrate Chez source from ober/ChezScheme to vendored jerboa/sr.ht

ober

118c225cf4c5c447616cecc2f1de2b134ab2f7be

diff --git a/Dockerfile b/Dockerfile
index 7412010..4293942 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -41,19 +41,18 @@ ENV HOME=/build
 WORKDIR /build
 
 # ── Build Chez Scheme (stock glibc, for compilation steps) ───────────────────
-RUN git clone --depth 1 https://github.com/ober/ChezScheme.git && \
-    cd ChezScheme && \
-    git submodule update --init --depth 1 && \
+# Chez is now vendored inside jerboa at vendor/ChezScheme.
+RUN git clone --depth 1 https://git.sr.ht/~lisp/jerboa /tmp/jerboa-src && \
+    cd /tmp/jerboa-src/vendor/ChezScheme && \
     ./configure --threads --disable-x11 --installprefix=/usr/local && \
     make -j$(nproc) && \
     make install && \
-    cd /build && rm -rf ChezScheme
+    cd /build && rm -rf /tmp/jerboa-src
 
 # ── Build Chez Scheme (musl, for static linking) ────────────────────────────
 # Two passes: glibc for boot files, then musl for libkernel.a
-RUN git clone https://github.com/ober/ChezScheme.git chez-musl-src && \
-    cd chez-musl-src && \
-    git submodule update --init && \
+RUN git clone https://git.sr.ht/~lisp/jerboa /tmp/jerboa-musl-src && \
+    cd /tmp/jerboa-musl-src/vendor/ChezScheme && \
     ./configure --threads --disable-x11 --installprefix=/build/chez-musl && \
     make -j$(nproc) && \
     cp ta6le/boot/ta6le/petite.boot /tmp/petite.boot && \
@@ -65,12 +64,12 @@ RUN git clone https://github.com/ober/ChezScheme.git chez-musl-src && \
     cp /tmp/scheme.boot ta6le/boot/ta6le/ && \
     make -j$(nproc) kernel && \
     make install && \
-    cd /build && rm -rf chez-musl-src /tmp/petite.boot /tmp/scheme.boot
+    cd /build && rm -rf /tmp/jerboa-musl-src /tmp/petite.boot /tmp/scheme.boot
 
 # ── Clone jerboa framework ──────────────────────────────────────────────────
 WORKDIR /build/mine
 ARG JERBOA_CACHE_BUST=1
-RUN git clone --depth 1 https://github.com/ober/jerboa.git && echo "bust=$JERBOA_CACHE_BUST"
+RUN git clone --depth 1 https://git.sr.ht/~lisp/jerboa && echo "bust=$JERBOA_CACHE_BUST"
 
 # ── Patch jerboa-native-rs with files not yet pushed to remote ──────────────
 # x25519.rs, process_ctl.rs, updated Cargo.toml/lib.rs needed for secmon