fix(sdk): preserve client accessors through extend() - #488

Summary

client.extend() built the extended object with a shallow spread:

const extended = { ...base, ...extensions }

config and providers are accessor properties. A spread evaluates them and writes their current values as plain data properties, so the extension stops tracking the client. Because setProviders reassigns _providers rather than mutating it, an extended client is pinned to whatever the provider list was at extend time.

Verified against the published @lifi/sdk@4.8.0 dist:

base.providers      : [{"type":"EVM"}]
extended.providers  : []
extended.getProvider: undefined
providers is getter on extended? false

So a host that extends before registering its wallet providers gets a client whose getProvider always returns undefined — execution can never run. Chain and RPC storage were unaffected, because setChains/getChains/getRpcUrls close over _storage rather than going through an accessor.

Changes

• createClient.ts: copy property descriptors instead of spreading, so the base and every extension share one live view of config and providers.
• createClient.unit.spec.ts: two failing-first tests — providers registered after the extension is created, and base/extension sharing one list.
• getRoutes.unit.spec.ts: lock request-level attribution precedence. Once a host and a widget share a client, the client carries the host's integrator, referrer and fee, so every caller that needs its own must send them with the request. These pin that contract.

Testing steps

pnpm test — 249 tests pass. biome, tsc, circular-deps and knip all clean via the pre-commit gate.

Why did I implement it this way?

Descriptor copying is the minimal change that keeps extend's existing shape and semantics. The alternative — making setProviders mutate the array in place — would fix the symptom but leave config still copied by value.

Context

Found while investigating JUM-1527 (deduplicating the SDK bootstrap between the Jumper app and the widget). The extend-based approach was the obvious way to share a client between a host and a widget, and this is why it did not work.