feat(ci): build the linux-arm64 native for the .NET and JVM bindings

[ayushthakur18]

Closes #18.

Problem

The chat_xdk_dotnet cdylib ships for osx-arm64, osx-x64, linux-x64 and win-x64. There is no linux-arm64, so the JVM and .NET bindings cannot run on 64-bit ARM Linux — AWS Graviton, Ampere, and ARM CI runners.

On Linux/aarch64, detectRid() returns null, so extractBundledLibrary() extracts nothing and load() falls through to a system lookup that finds nothing unless the operator supplies their own build.

Because dotnet-build also feeds the java job, this single missing matrix entry affects both bindings.

Change

• one linux-arm64 entry in the dotnet-build matrix, on ubuntu-24.04-arm targeting aarch64-unknown-linux-gnu
• linux-arm64 staged alongside the other RIDs for both the nupkg and the jar
• native/linux-arm64/libchat_xdk_dotnet.so added to the jar verification list, so a missing artifact fails the release rather than shipping silently
• detectRid() returns linux-arm64 on Linux/ARM

The ubuntu-24.04-arm runner and the aarch64-unknown-linux-gnu target are already used by the Python wheel job in this same workflow, so nothing new is introduced to CI.

Verification

Built chat-xdk-dotnet for aarch64-unknown-linux-gnu from v0.5.0, with juicebox-sdk as a sibling checkout and the pinned 1.91.1 toolchain:

Finished `release` profile [optimized] target(s) in 1m 25s
libchat_xdk_dotnet.so: ELF 64-bit LSB shared object, ARM aarch64, version 1 (SYSV), dynamically linked

Loaded through JNA on an ARM64 JVM (Temurin 25), with no jna.library.path set, to confirm the resource path detectRid() now returns is the one JNA resolves:

arch=aarch64
RESOURCE_PREFIX=linux-aarch64
LOADED OK: true

I have not been able to run the full release workflow, so the matrix entry itself is unexercised — the build and load above were reproduced locally against the same source and toolchain.

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