ci: upload lib-vt source tarball to R2

Add R2 upload steps to the source-tarball-lib-vt job in the tip
release workflow, matching the pattern used by the xcframework
job. The tarball is uploaded to the ghostty-tip R2 bucket keyed
by commit hash, making it available at
tip.files.ghostty.org/<commit>/libghostty-vt-source.tar.gz.

.github/workflows/release-tip.yml

@@ -219,6 +219,7 @@ jobs:
       )
     runs-on: namespace-profile-ghostty-sm
     env:
+      GHOSTTY_COMMIT_LONG: ${{ needs.setup.outputs.commit_long }}
       ZIG_LOCAL_CACHE_DIR: /zig/local-cache
       ZIG_GLOBAL_CACHE_DIR: /zig/global-cache
     steps:
@@ -260,6 +261,25 @@ jobs:
             libghostty-vt-source.tar.gz.minisig
           token: ${{ secrets.GH_RELEASE_TOKEN }}
 
+      - name: Prep R2 Storage
+        run: |
+          mkdir -p blob/${GHOSTTY_COMMIT_LONG}
+          cp libghostty-vt-source.tar.gz blob/${GHOSTTY_COMMIT_LONG}/libghostty-vt-source.tar.gz
+      - name: Upload to R2
+        uses: ryand56/r2-upload-action@b801a390acbdeb034c5e684ff5e1361c06639e7c # v1.4
+        with:
+          r2-account-id: ${{ secrets.CF_R2_TIP_ACCOUNT_ID }}
+          r2-access-key-id: ${{ secrets.CF_R2_TIP_AWS_KEY }}
+          r2-secret-access-key: ${{ secrets.CF_R2_TIP_SECRET_KEY }}
+          r2-bucket: ghostty-tip
+          source-dir: blob
+          destination-dir: ./
+
+      - name: Echo Release URLs
+        run: |
+          echo "Release URLs:"
+          echo "  Source Tarball: https://tip.files.ghostty.org/${GHOSTTY_COMMIT_LONG}/libghostty-vt-source.tar.gz"
+
   build-lib-vt-xcframework:
     needs: [setup]
     if: |