fix(android): bake android24→26 clang shim into the docker image itself

Build #13's PATH wrapper trick failed because tauri-cli invokes the linker
with an absolute path (/opt/android-sdk/ndk/.../bin/aarch64-linux-android24-
clang), which bypasses \$PATH entirely. The pthread_shim logs confirmed the
broken API-24 stubs were still being linked:

  WZP_pthread_shim: dlsym(RTLD_DEFAULT, pthread_create) returned NULL:
    libdl.a is a stub --- use libdl.so instead

Move the fix up a level — into the Dockerfile itself. On image build, for
each of the four android ABIs × {clang, clang++}, rename
`${abi}24-${suffix}` to `${abi}24-${suffix}.orig` and replace it with a
shell wrapper that exec()s `${abi}26-${suffix}`. Any call to the API-24
wrapper — via PATH, absolute path, or otherwise — now transparently runs
the API-26 wrapper, which uses the real libc.so/libdl.so bindings.

The old bash-c /tmp/wrappers workaround in build-tauri-android.sh is
removed now that the image handles it at the right layer.

Also add `--shell` to build-tauri-android.sh: opens an interactive docker
container on the remote with the same mounts/env as the build, so I can
iterate on cargo tauri android build / manually patch files / etc.
without the full git push → ssh → rebuild → install loop.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/Dockerfile.android-builder

@@ -74,6 +74,27 @@ RUN yes | $ANDROID_HOME/cmdline-tools/latest/bin/sdkmanager --licenses > /dev/nu
         "platform-tools" \
         2>&1 | grep -v '^\[' > /dev/null
 
+# Work around broken API-24 libc/libdl stubs in the NDK. Rust's pre-compiled
+# libstd.rlib for aarch64-linux-android links against pthread_create / dlsym
+# from the sysroot. With --target=...24, those resolve to the API-24 "stub"
+# libc.a/libdl.a that return "libdl.a is a stub --- use libdl.so instead" at
+# runtime. API-26 has real dynamic bindings. Tauri-cli hard-codes the
+# android24-clang path so env var overrides don't stick.
+#
+# Permanent fix inside the image: replace every `${abi}24-clang` binary with
+# a shim that exec()s the corresponding `${abi}26-clang`. Any build using
+# this image now transparently gets the API-26 sysroot even when the caller
+# asks for API-24.
+RUN set -eux; \
+    BIN=$ANDROID_NDK_HOME/toolchains/llvm/prebuilt/linux-x86_64/bin; \
+    for abi in aarch64-linux-android armv7a-linux-androideabi i686-linux-android x86_64-linux-android; do \
+        for suffix in clang clang++; do \
+            mv "$BIN/${abi}24-${suffix}" "$BIN/${abi}24-${suffix}.orig"; \
+            printf '#!/bin/sh\nexec "%s/%s26-%s" "$@"\n' "$BIN" "$abi" "$suffix" > "$BIN/${abi}24-${suffix}"; \
+            chmod +x "$BIN/${abi}24-${suffix}"; \
+        done; \
+    done
+
 # Make SDK world-readable so builder user can access it
 RUN chmod -R a+rX $ANDROID_HOME