sdk: add website metadata and fix ARM64 runner label

Add website field to sdkcraft.yaml pointing to the GitHub repository.

Switch the ARM64 CI runner from ubuntu-24.04-arm64 to ubuntu-26.04-arm
(alternate label per GitHub's public preview docs), keeping amd64 on
ubuntu-24.04.

Author: rajannpatel

.github/workflows/upload.yml

@@ -23,7 +23,7 @@ jobs:
           - platform: '["amd64"]'
             runner: '["ubuntu-24.04"]'
           - platform: '["arm64"]'
-            runner: '["ubuntu-24.04-arm64"]'
+            runner: '["ubuntu-26.04-arm"]'
     uses: canonical/sdkcraft-actions/.github/workflows/upload.yml@main
     with:
       platforms: ${{ matrix.platform }}

sdkcraft.yaml

@@ -8,6 +8,7 @@ description: |
 contact: https://github.com/rajannpatel/agy-sdk
 issues: https://github.com/rajannpatel/agy-sdk/issues
 source-code: https://github.com/rajannpatel/agy-sdk
+website: https://github.com/rajannpatel/agy-sdk
 adopt-info: agy
 license: MIT AND Proprietary
 build-base: ubuntu@26.04