chore(admin): move admin reads to gRPC and drop the JSON-RPC client

[11felix]

Removes the JSON-RPC client from this SDK. Four admin helpers were the only remaining users; they now read over gRPC, so pythSuiClient and the @mysten/sui/jsonRpc dependency are gone.

Motivation: JSON-RPC is deprecated on Sui public fullnodes, and keeping it meant every consumer had to configure a second endpoint for these four functions alone.

Migrated

Function	Was	Now
getRebalanceCap	getOwnedObjects({filter: {StructType}})	core.listOwnedObjects({owner, type})
addExternalRewardsWalLockedTxb	getOwnedObjects({filter: {MoveModule}}) + client-side type filter	core.listOwnedObjects on the exact AdminCap type
getWithdrawRequestsAndUnsuppliedAmount	getObject({showContent})	core.getObject({include: {json}})
getWalLockedRewardInfo	getObject({showContent})	core.getObject({include: {json}})

The two getObject sites needed re-parsing, not just a transport swap: JSON-RPC wraps nested Move structs as {type, fields: {...}} while gRPC renders them flat. Scalars are identical.

Verified against mainnet — both parsers run side by side on the live objects, output compared:

alphaVault requests: 4
alphaVault PARITY: IDENTICAL
WAL rewards PARITY: IDENTICAL

The AlphaVault pool had 4 real withdraw requests at the time, so the nested VecMap path (contents[].key / contents[].value.leftover_amount) is exercised rather than short-circuiting on an empty list — worth stating because the failure mode here is silent: the old ?.fields?.contents ?? [] against a flat payload yields [] and renders an empty screen with no error.

getWalLockedRewardInfo already had ?? fallbacks that tolerated both shapes, so it was correct either way; it is now written for the one shape it uses.

Also: grpcUrl is plumbed through AlphaFiSDKConfig → StrategyContext → Blockchain, so consumers can point object reads at their own endpoint instead of the built-in public-fullnode default. It was previously reachable only by mutating blockchain.suiGrpcClient after construction, and not at all through AlphaFiSDK, whose strategyContext is private.

graphqlUrl is untouched — rpcpool does not serve the Sui GraphQL schema, so gqlClient cannot move with the rest.

Breaking: Blockchain.pythSuiClient and BlockchainOptions.pythSuiClient are removed. alphafi-admin is the only consumer I found; its matching change is in alphafi-admin#33.

tsc --noEmit, npm run build and the pre-commit hooks are clean. npm test reports no tests configured.