Feat/hyperbridge onboarding

[nol4lej]

What

Two corrections found while onboarding Orbinum onto Hyperbridge's Paseo testnet.

The Paseo relayer config was missing slot_duration. Tesseract's HostConfig (tesseract/consensus/grandpa/src/lib.rs:85) declares it without a default, so the relayer aborted with missing field slot_duration before connecting to anything. The local config had it; the production template did not, which is why local validation never caught this. Added to both sections, along with the consensus_update_frequency their docs specify.

The fee model was documented backwards. The comments claimed a zero relayer fee would let anyone "give away work to a third party", and that opening DispatchOrigin required deciding a price first. Hyperbridge's fee docs and their own dispatcher say otherwise:

// modules/pallets/ismp/src/dispatcher.rs:98
if fee.fee != Zero::zero() {
    T::Currency::transfer(&fee.payer, &RELAYER_FEE_ACCOUNT..., fee.fee, ...)
}

With a zero fee nothing is transferred and nobody is owed. The real effect is that Hyperbridge's permissionless relayers won't deliver, they prioritise by fee. Orbinum self-relays, which their docs call the intended integration, so zero is the correct value, not a placeholder.

Also corrected: POLICY = false on the FeeHandler was described as disabling relayer fees. It governs the inbound side, whether whoever submits an incoming message pays its execution weight. Unrelated to the outbound relayer fee in FeeMetadata.

Impact

Comments and one config file. No code changes — git diff on the Rust files is entirely // lines.

Onboarding status

Done on-chain with these fixes, verified live on testnet:

consensusStates(PAS0):  2298 bytes
supportedStateMachines: { "kusama": 4009 } → slot 6000
challengePeriod:        0s

Hyperbridge → Orbinum verifies now. The other direction waits on polytope-labs/hyperbridge#1200, which only they can action.