Extract intent library, migrate wallet connector, and overhaul test suite

[reednaa]

Summary

• Extract @lifi/intent package: Core logic from the monolithic intent.ts (923 lines) and orderServer.ts (564 lines) has been extracted into an external @lifi/intent package. Utility functions (idLib, convert, typedMessage, interopableAddresses, orderLib) are now consumed from the package rather than maintained locally.
• Split remaining library code: What stays in the app is reorganised into focused modules — intentExecution.ts (signing & on-chain execution), intentFactory.ts (order construction), and coreDeps.ts (oracle/settler dependency injection).
• Migrate wallet connector: Replaced web3-onboard with wagmi (wagmi.ts, walletClient.ts, walletClientRuntime.ts). Chain switching and wallet signing now go through wagmi hooks.
• Chain ID migration: Removed chain-string identifiers throughout in favour of numeric chainId values, aligning with viem/wagmi conventions.
• E2E test suite: Added full end-to-end tests for the standard escrow order flow — both a blackbox variant (mock allocator) and a live variant — with a shared bootstrap helper.
• Unit tests: Added unit tests covering intentList, orderValidationDeps, and wallet-client chain switching. Removed stale orderLib, orderServer, and issuance tests that tested now-extracted code.
• Monorepo reverted: A mono-repo structure was introduced and then collapsed — the lintent app is back at the top level with a cleaned-up package.json and bun.lock.

Test plan

• bun test — all unit tests pass
• bun run test:e2e with .env.e2e populated — blackbox E2E passes
• Manually exercise connect-wallet → issue intent → fill intent → finalise flow in the browser
• Confirm wagmi wallet connector works across supported chains (chain switching, signing)