fix(web3-compat): correct types export path in declaration build

[tylerthebuildor]

Summary

• @solana/web3-compat declares its types at ./dist/types/index.d.ts, but the declaration build actually outputs to ./dist/types/web3-compat/src/index.d.ts. TypeScript can't resolve the module without a manual .d.ts shim.
• The root cause is that tsconfig.declarations.json inherits a paths mapping from tsconfig.json that points @solana/client at raw .ts source files in ../client/src/. This pulls the full client source tree into the program, widening the computed rootDir and nesting the output.
• Fix: override paths in the declarations tsconfig to resolve @solana/client from its built .d.ts files. This is the same pattern used by react-hooks (added in 6cdb52a).
• Also adds @solana/web3-compat to the type smoke tests so this gets caught by CI going forward.

Testing

• pnpm lint
• pnpm test
• pnpm build
• pnpm --filter @solana/test-types-smoke test
• Verified dist/types/index.d.ts exists after build (previously only dist/types/web3-compat/src/index.d.ts existed)

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