Support Temurin on Linux RISC-V (#1269)

* Document Temurin RISC-V compatibility

Co-Authored-By: multicode <multicode@yawk.at>

* Expose RISC-V as a canonical architecture

Co-Authored-By: multicode <multicode@yawk.at>

* Support Temurin on Linux RISC-V

Co-Authored-By: multicode <multicode@yawk.at>

* Address RISC-V review feedback

Co-Authored-By: multicode <multicode@yawk.at>

* Fix casing for RISC-V architecture in tests

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* Update __tests__/java-platform-contract.test.ts

---------

Co-authored-by: multicode <multicode@yawk.at>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

__tests__/distributors/temurin-installer.test.ts

@@ -293,7 +293,8 @@ describe('getAvailableVersions', () => {
   it.each([
     ['amd64', 'x64'],
     ['arm', 'arm'],
-    ['arm64', 'aarch64']
+    ['arm64', 'aarch64'],
+    ['riscv64', 'riscv64']
   ])(
     'defaults to os.arch(): %s mapped to distro arch: %s',
     async (osArch: string, distroArch: string) => {

__tests__/java-platform-contract.test.ts

@@ -25,6 +25,7 @@ describe('Java platform capabilities', () => {
     ['aarch64', 'aarch64'],
     ['arm64', 'aarch64'],
     ['ppc64le', 'ppc64le'],
+    ['RiScV64', 'riscv64'],
     ['s390x', 's390x']
   ])('normalizes architecture %s to %s', (input, expected) => {
     expect(normalizeArchitecture(input)).toBe(expected);
@@ -68,6 +69,12 @@ describe('Java platform capabilities', () => {
     );
   });
 
+  it('allows Temurin on Linux riscv64', () => {
+    expect(validateJavaPlatform('temurin', 'linux', 'riscv64', '25')).toBe(
+      'riscv64'
+    );
+  });
+
   it('rejects OS-specific restrictions with a consistent diagnostic', () => {
     expect(() =>
       validateJavaPlatform('oracle', 'win32', 'arm64', '21')
@@ -115,6 +122,7 @@ describe('Java platform capabilities', () => {
         'aarch64',
         'ppc64le',
         'ppc64',
+        'riscv64',
         's390x'
       ]) {
         expect(content).toContain(architecture);