Widget: make optional peer dependencies actually optional

[linear]

Problem

packages/swap-widget/package.json marks seven peers optional: true in peerDependenciesMeta. The intent is graceful degradation — a consumer who doesn't install the Solana or Bitcoin packages simply doesn't get those wallets.

That isn't what happens. Every one of the seven is reached by a static value import from the single src/index.ts entrypoint, and tsup emits one flat ESM bundle with all of them marked external. The specifiers sit at the top of dist/index.js, so the consumer's bundler has to resolve them whether or not they ever touch Solana. An EVM-only integrator following the documented install list gets a module resolution failure, not a widget with Solana quietly switched off.

Audit

optional peer	static value import	reachable from entrypoint via
@reown/appkit	WalletProvider.tsx:1, SwapWidget.tsx:3	direct
@reown/appkit-adapter-wagmi	config/appkit.ts (WagmiAdapter)	SwapWidget → WalletProvider → appkit
@reown/appkit-adapter-bitcoin	config/appkit.ts (BitcoinAdapter)	same
@reown/appkit-adapter-solana	config/appkit.ts (SolanaAdapter), useBalances.ts:1, useSolanaSigning.ts:3	same + TokenSelectModal
@solana/web3.js	useBalances.ts:3, utils/addressValidation.ts:2	SwapWidget.tsx:23 → validateAddress
@solana/wallet-adapter-phantom	config/appkit.ts	SwapWidget → WalletProvider → appkit
@solana/wallet-adapter-solflare	config/appkit.ts	same

ESM imports are hoisted and eagerly resolved, so it doesn't help that new PhantomWalletAdapter() only runs inside initializeAppKit() — the import is resolved at module load regardless of whether that function is ever called.

Note that someone already reached for the right technique: useSwapExecution.ts:84 and :156 do await import('@solana/web3.js'). It buys nothing today, because utils/addressValidation.ts:2 value-imports PublicKey from the same package and SwapWidget.tsx:23 pulls that in unconditionally. The lazy path is defeated by a static one two files over.

Options

1. Separate entrypoint — move the AppKit/Solana surface behind @shapeshiftoss/swap-widget/appkit (or similar) that consumers opt into via exports. Cleanest signal, but changes the package's public shape and the integration docs.
2. Dynamic imports throughout — convert the adapter construction and the PublicKey/Connection uses to await import(...), guarding the optional-peer paths. Keeps one entrypoint; needs the addressValidation/useBalances call sites to tolerate async.

Either way the install snippets in packages/swap-widget/README.md and packages/public-api/docs/swap-widget-sdk.md need to say which packages are genuinely required for which chain families.

Context

Surfaced during review of #12601, which swapped @solana/wallet-adapter-wallets for the two adapters actually used. That PR doesn't change this situation — one non-functional optional marking became two, contract identical — and its description calls the underlying problem out as a known follow-up. CodeRabbit flagged the two adapters on that PR and was told the same; marking just those two required would have fixed nothing while the other five static imports remained.

Related: @shapeshiftoss/caip statically bundles the generated CoinGecko/CoinCap maps for every chain (~807 KB gzipped, Base alone ~179 KB), which is a similar all-or-nothing weight problem for chain-scoped integrators.