feat(sdk-coin-tao): build claimRootWithHotkey extrinsic from intent

[bitgo-ai-agent-dev]

What

• abstract-substrate: add ClaimRootWithHotkey to MethodNames const, add ClaimRootWithHotkeyArgs interface ({ hotkey: string }) to iface.ts TxMethod.args union, add ClaimRootWithHotkeyTransactionSchema joi schema
• sdk-coin-tao: new ClaimRootBuilder — builds SubtensorModule.claimRootWithHotkey(hotkey) extrinsic via defineMethod; implements hotkey() setter, buildTransaction(), fromImplementation(), validateTransaction(), validateDecodedTransaction()
• sdk-coin-tao: new ClaimRootTransaction — overrides toJson() (adds hotkey field), loadInputsAndOutputs() (populates _outputs with hotkey address, resets arrays before repopulating), explainTransaction()
• sdk-coin-tao: new ClaimRootTxData interface in iface.ts
• sdk-coin-tao: TransactionBuilderFactory — register ClaimRootWithHotkey dispatch in getBuilder() and expose getClaimRootBuilder()
• sdk-coin-tao: Tao.verifyTransaction override — short-circuits for StakingClaim type (case-insensitive) before the parent tries to access _to/_amount which don't exist on ClaimRootBuilder
• sdk-coin-tao: new src/resources/testnetV2.ts — Bittensor testnet metadata (specVersion 443) that includes claim_root_with_hotkey; existing testnet.ts (specVersion 224) unchanged
• sdk-coin-tao: wire TaoClaimRootIntent { hotkey, netuid: 0 } end-to-end in tao.ts
• Unit tests: unsigned build, signed build, round-trip from(), factory dispatch, outputs content, loadInputsAndOutputs null-safety, explainTransaction, validation, error paths, verifyTransaction with both PascalCase and lowercase type

Why

• SI-1171 requires sdk-coin-tao to accept TaoClaimRootIntent { hotkey, netuid: 0 } and produce a signed, broadcastable SubtensorModule.claimRootWithHotkey extrinsic. This is a P0 blocker for the TAO Root Reborn claim feature and directly blocks SI-1172 ([WP] Route CLAIM_REWARDS request type for tao/ttao)

Test plan

• mocha — 93 passing, 2 pending, 1 pre-existing failure (requires BITGOJS_TEST_PASSWORD)
• TypeScript build: sdk-coin-tao and abstract-substrate compile clean
• loadInputsAndOutputs resets _outputs/_inputs before push — idempotent on repeated build() calls
• verifyTransaction uses case-insensitive comparison — handles WalletPlatform lowercase 'stakingclaim' intentType
• Integration test on testnet after feature is wired end-to-end (SI-1172)

Ticket: SI-1171

[linear-code]

SI-1171

[abhijit0943]

Review

Recommend: request changes — one real correctness/security issue in verifyTransaction; rest of the builder/transaction implementation follows the existing MoveStakeBuilder pattern closely and has solid test coverage.

Critical

modules/sdk-coin-tao/src/tao.ts:319-326 — the new verifyTransaction override returns true for any stakingclaim-typed request without ever decoding txPrebuild.txHex. That skips all validation, not just the recipient/amount check the comment claims to be avoiding.

• The stated reason ("parent tries to access _to/_amount which don't exist on ClaimRootBuilder") doesn't hold up — reading an undefined property in JS returns undefined, it doesn't throw.
• The base SubstrateCoin.verifyTransaction already handles this safely: when txParams.recipients is undefined (true for claim/staking intents), it falls through to return true, but only after calling factory.from(txPrebuild.txHex) to decode the tx. MoveStakeBuilder/StakingBuilder/UnstakeBuilder all lack _to/_amount too and never needed a Tao-level override for this.
• DOT (same abstract-substrate family) has a ClaimBuilder for claim rewards and does zero special-casing — same recipients === undefined fallthrough, but it always calls factory.from() first.
• Net effect: a compromised/buggy WalletPlatform response tagged type: 'stakingclaim' carrying an arbitrary or malicious txHex (wrong hotkey, or not even a claim tx) would be approved for TSS signing with zero checks.

Suggested fix: drop the override — it should inherit the same safe fallthrough DOT and the other TAO builders already rely on.

Important

• claimRootTransaction.ts:186 — loadInputsAndOutputs() calls super.loadInputsAndOutputs(), which SCALE-decodes the tx a second time for nothing (the base dispatcher has no StakingClaim case), then decodes again itself. Redundant work, not a bug.
• utils.ts:8 — getMaterial() still points TESTNET at the old spec-224 testnetMaterial; the new testnetMaterialV2 (spec 443, has claim_root_with_hotkey) is only referenced by tests. Worth confirming this is intentionally deferred to SI-1172's end-to-end wiring rather than an oversight.

Minor

• Test comment at claimRootBuilder.ts:535 ("tip=0 is falsy → fallback fires") is inaccurate — (0).toString() is "0", a truthy string, so the || '0' never actually fires for tip=0. No functional impact, both branches yield '0'.

[abhijit0943]

lgtm