Exclude uncategorized channels from fee management and rebalancing

[markettes]

The engine now leaves channels alone until it has a committed flow verdict on them.
The fee optimizer filters them in OptimizeNode and writes no ChannelFeeState, so the
first managed cycle still seeds from the category baseline. The rebalancer drops them
in AutoRebalanceJob before building signals, so they are neither drained nor counted
toward a destination peer. Idle is a real verdict and stays fully managed.

Worth flagging explicitly in the PR body, since it's a deliberate trade rather than an oversight: filtering the channels out also hides their balance from the destination aggregate, so a peer with a mix of categorized and uncategorized channels can be over-refilled. It's pinned by Execute_MixedPeer_OverRefillsBecauseUncategorizedSiblingIsInvisible and written up in docs/rebalance-algorithm.md §8.

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