Recycle fees via chain ext with immutable custodial fallback

[LandynDev]

Summary

Wires the AddStakeRecycleV1 chain extension (subtensor PR #2560, function_id=18) into recycle_fees behind an owner-flipped one-way latch.

• Pre-latch: fees go to an immutable custodial fallback (recycle_address, set once in the constructor — no setter). The off-chain fee-recycler service in alw-utils picks them up and stakes them back to the subnet.
• Post-latch: fees dispatch through the chain extension to (staking_hotkey, netuid). Subtensor stakes-and-burns directly from the contract via add_stake_recycle.
• Latch flip: owner-only enable_chain_ext(), exposed as alw admin enable-chain-ext. Reverts if already set; emits ChainExtensionLatched { at_block } once.

Why owner-flip and not auto-probe-on-first-success

pallet-contracts traps the entire contract call when a chain extension returns Err(DispatchError) — which is exactly what subtensor returns for unknown function_ids on networks where PR #2560 hasn't landed yet (mainnet today). An auto-probing recycle_fees would revert before reaching its fallback branch, so fees would pile up in accumulated_fees until #2560 lands. Owner-flip sidesteps that entirely.

Verified mappings against subtensor PR #2560

• extension id 0x1000 matches subtensor-proxy registration
• function_id 18 matches FunctionId::AddStakeRecycleV1
• param order (AccountId, u16, u64) matches (AccountId, NetUid, TaoBalance) — both balance/netuid types are repr(transparent) newtypes with SCALE-equivalent encoding
• return u64 matches encoded alpha amount
• status code 0 = Success matches Output::Success

Contract

• New storage: staking_hotkey, netuid, chain_ext_enabled (constructor-set; only chain_ext_enabled mutates, via enable_chain_ext).
• recycle_fees stays permissionless; branches on chain_ext_enabled — chain ext only or env.transfer to recycle_address.
• New enable_chain_ext (owner-only, one-way).
• set_recycle_address removed.
• New getters: get_staking_hotkey, get_netuid, get_chain_ext_enabled.
• FeesRecycled gains via_chain_ext: bool; new ChainExtensionLatched { at_block } event.

Python / CLI

• contract_client.py: drop set_recycle_address; add the new getters, enable_chain_ext writer, u16 read primitive.
• admin.py: drop set-recycle-address; add enable-chain-ext (one-way confirm); recycle-fees UX shows pre/post-latch destination.
• view.py: alw view contract shows the recycle path (custodial vs chain ext) and the latch target.

Companion PR

alw-utils#45 wires staking_hotkey + netuid into the contract deployer, restores the off-chain fee-recycler for the pre-latch path, and renames --wallet-name → --owner-hotkey. Hard-blocked on this one.

Test plan

• cargo contract build --release clean
• pytest tests/ passes (387 cases)
• cd alw-utils/dev-environment && ./down.sh --force && ./up.sh --chains btc brings up the stack against the rebased deployer
• ./tests/run.sh --chains btc --suite 02 passes
• alw view contract shows pre-latch path with custodial address + latch target row
• alw admin recycle-fees (pre-latch) transfers to recycler wallet; recycler service stakes back
• alw admin enable-chain-ext flips latch; second call errors out
• alw admin recycle-fees (post-latch) routes through chain extension; via_chain_ext = true in event