feat(sdk-core): add typed sysio.chains registry client

[joshglogau]

Summary

Adds a typed sysio.chains SDK client so consumers can discover the protocol's registered external chains through the same system-contract architecture used by AuthEx, multisig, and reserves.

What changed

• registers sysio.chains in the shared system-contract descriptor registry
• adds a typed ChainsClient backed by the generic contract proxy
• exposes raw paginated chain-table reads and normalized chain records
• supports filtering by activation state, depot state, signing family, and result limit
• decodes packed slug_name chain codes into stable values such as ETHEREUM and SOLANA
• normalizes generated enum responses and lifecycle timestamps for application consumers
• adds unsigned regchain and activchain action builders
• documents both the domain facade and lower-level proxy access
• adds focused coverage for action construction, pagination/filtering, normalization, and slug conversion

Why

Applications should derive protocol availability and signing-family information from sysio.chains instead of maintaining a duplicated hardcoded registry. RPC URLs, explorers, wallet adapters, icons, and application-specific capabilities remain outside the SDK and can be layered on by each consumer.

Compatibility

This is additive. Existing sdk-core clients and exports are unchanged.

Validation

• pnpm run compile
• pnpm exec jest packages/sdk-core/tests/contracts/sysio/chains --runInBand
• 3 suites passed, 9 tests passed