feat(consensus): finalize DKG speculatively

[SuperFluffy]

Changes DKG finalization to work on notarized blocks.

Tempo wants to finalize its DKG ceremony and include the outcome in the boundary block of each epoch. With this patch, the application actor requests the DKG outcome based on the boundary block's parent digest. The DKG manager then decides whether it can already construct the outcome of the DKG ceremony (because it has already finalized the pre-to-boundary block), or if it has to first fetch notarized blocks and construct the outcome based on those.

Before this patch, the DKG actor would only construct the DKG outcome upon finalization of the pre-to-boundary block. But because simplex gives no guarantees about observing direct finalizations of all blocks, this could lead to chain halts in certain edge cases (network instability comes to mind).

With this patch the node no longer persists the dealings it finds in finalized blocks. Instead, on restart it backfills them from the marshal actor.

Closes #924

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Project	Deployment	Review	Updated (UTC)
tempo-docs	Ready	Preview, Comment	Dec 17, 2025 11:13am