ILGPU v2.0: AOT + Cross-Platform Native SDK Support

[m4rs-mt]

This PR introduces the bridge between the new AOT compiler and the vendor-specific native toolchains (CUDA's nvcc, Apple's metal, AMD's hipcc, Intel's ocloc, clang), plus a remote compilation service that exposes the compiler over HTTP so CI jobs and developers without local GPU toolchains can offload PTX/Metal-IR/HIP generation.

This PR is intentionally kept small: Docker images, test suite, CI redesign, and samples all land in the follow-up PRs so that reviewers of this PR can focus on the backend-infrastructure code itself.

The first two commits are PR placeholders (for the runtime-library PR and the AOT-compiler PR); once those land on master they collapse into real merge commits.

A note on authorship - AI warning

Some bits of the compiler-service work in this PR was done with AI-assistant pair programming (Claude via Claude Code).

What's in this PR

Native compiler bindings (Src/ILGPUC.Compilers/, 17 files)

Thin managed wrappers around the vendor toolchains. Each wrapper handles tool discovery, argument construction, subprocess invocation, and result parsing so ILGPUC can invoke them with a uniform API:

• MetalCompiler — wraps Apple's xcrun metal.
• NvccCompiler — wraps NVIDIA's nvcc.
• HipccCompiler — wraps AMD's hipcc.
• OclocCompiler — wraps Intel's OpenCL offline compiler.
• ClangOpenCLCompiler — wraps clang -x cl for OpenCL-on-anything fallback.

Around them: CompilerBase, CompilerManager, CompilerOptions, CompileRequest, CompilationResult, CompilationTarget, CompilationCapabilities, ICompiler, ICompilerManager, OutputType, ToolchainComponent.

Remote compilation service (Src/ILGPUC.CompilerService/, 16 files)

An ASP.NET Core service that exposes the compiler over HTTP:

• Program.cs — host bootstrap and service wiring.
• Controllers — CompileController (fire-and-forget compile), JobsController (async compile queue), CapabilitiesController (report which backends this host supports), StatusController (health / readiness), BaseApiController.
• Jobs — CompilationJob, IJobQueue, JobQueue for async queued compilation.
• Caching — CompilationCache, ICache so identical kernels don't get recompiled across requests.
• Models — JobEnqueueResponse, StatusResponse, ErrorResponse DTOs.
• appsettings.json — default configuration.

CompilerService tests (Src/ILGPUC.CompilerService.Tests/, 11 files)

Integration-level coverage for every endpoint:

• Fixtures — MockServiceFixture spins up the service in-process for xUnit; Mocks/MockCompilerManager lets tests run without the actual native toolchains installed.
• Endpoint tests — CompileEndpointTests, JobEndpointTests, StatusEndpointTests, CapabilitiesEndpointTests, CompileErrorTests.
• Scenario tests — CachingTests (cache hit/miss behaviour), RemoteCompilerIntegrationTests (full round-trip through the async job queue).
• ILGPUC.CompilerService.Tests.csproj, GlobalUsings.cs.

Solution and shared-config wiring

• Src/ILGPU.sln registers the three new projects (ILGPUC.Compilers, ILGPUC.CompilerService, ILGPUC.CompilerService.Tests).
• Src/.editorconfig, Src/Directory.Build.props, global.json, .gitignore are synchronized with the ILGPUC tooling target framework.

Scope boundary

No changes to Src/docker/, Src/scripts/, any GitHub workflow file, Src/ILGPUC.Tests/, .gitmodules, Src/CLAUDE.md, or Samples/. Those land in follow-up PRs.

Depends on

PR #1577

Fixes

Closes #1542.