fix(ci): release asset upload must be POST multipart, not PUT

curl --upload-file issues a PUT, which Forgejo answers with 405 -- the
attach-MSI step would have failed on every release. Switch to
-X POST -F attachment=@file and fail the step on curl errors instead of
masking them.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.forgejo/workflows/release.yml

@@ -206,11 +206,13 @@ jobs:
               -ContentType 'application/json' -Body $body
           }
 
-          # Upload the MSI as an asset.
+          # Upload the MSI as an asset. Must be POST multipart/form-data —
+          # curl's --upload-file does a PUT, which Forgejo answers with 405
+          # (verified against Forgejo 2026-07-06 while shipping 1.2.0-beta.1).
           $uploadUri = "$env:FORGE_API/releases/$($release.id)/assets?name=$env:MSI_NAME"
-          curl.exe -fSL `
+          curl.exe -fSL -X POST `
             -H "Authorization: token $env:FORGE_TOKEN" `
-            -H "Content-Type: application/octet-stream" `
-            --upload-file "$env:MSI_PATH" `
+            -F "attachment=@$env:MSI_PATH" `
             "$uploadUri"
+          if ($LASTEXITCODE -ne 0) { throw "asset upload failed (curl exit $LASTEXITCODE)" }
           Write-Host "Asset $env:MSI_NAME attached to release $env:TAG."