Restore Uint8Array pubkeys after localStorage round-trip

[Steve0x2a]

JSON.stringify/parse in LocalStorage turned Uint8Array pubkeys into {0:…,1:…} objects. After a reload, WalletManagerStore.restore() loaded that state unchanged and ChainWalletStore.getAccount() returned the cached account, so signing failed with "length of pubkey is incorrect".

LocalStorage.load() now revives those numeric-key objects back into Uint8Array, so every consumer of persisted store state gets a real pubkey.

Thanks @drimchansky for reporting this in #40.

Fixes #40.

[devin-ai-integration]

LGTM — thanks for the fix and for the thorough tests; sorry for the wait. Reviving at the LocalStorage.load() boundary is the right place: WalletManagerStore.restore() consumes that output directly, so every consumer of persisted chainWalletStates gets a real Uint8Array back (fixes #40). The revivePubkey helper correctly handles both the { "0": 1, "1": 2, ... } JSON shape and an already-typed array, and the account mapping leaves other fields untouched.

Verified on a local merge onto current main: pnpm install, pnpm build, pnpm test all pass (store 176/176, incl. the new save/load round-trip test); eslint src __tests__ in packages/store shows the same pre-existing issues as main, nothing new. Merges cleanly together with #39, #42 and #44.

Reviewed by Devin on behalf of @pyramation