browser/openspec/changes/fix-scum-run-distribution-smoke/proposal.md

Why

The local debug SCUM fixture can be registered with a reduced manifest that omits server.run.distribution. That makes scum-alpha visible and manageable, but POST /api/v1/server-instances/scum-alpha/run/generate is denied even though the first-party SCUM manifest declares run distribution support.

What Changes

• Register the local debug SCUM plugin with the run distribution, dependency, client-manager, bridge, and remote-access declarations from the first-party manifest.
• Extend local debug smoke proof to verify generate-run is available for scum-alpha.
• Extend local debug smoke proof to generate a Windows AMD64 run distribution for scum-alpha.
• Make deterministic run generation recover from an already-created package artifact instead of surfacing duplicate_resource to the UI.
• Make repeated run self-update dispatches return the existing update job when the artifact/checksum/idempotency key match.

Impact

• Affected specs: scum-run-distribution-smoke
• Affected code: scripts/local-debug-smoke.sh, platform/service/distributions.go