refactor: add builders of transaction

[anyxem]

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[Copilot]

Pull Request Overview

This PR refactors the SDK client by extracting transaction construction into build* methods and updating existing methods to call these builders before signing. It centralizes transaction creation, clarifies returns, and adapts JSDoc accordingly.

• Introduce build* methods for all transaction types, returning unsigned Transaction objects.
• Update original methods to call the new builders and then sign the transaction.
• Adjust JSDoc comments to describe unsigned return values for builders.

Comments suppressed due to low confidence (1)

packages/sdk/src/mintlayer-connect-sdk.ts:2587

• Add a @returns annotation to this JSDoc comment to specify that it returns an unsigned Transaction object, keeping it consistent with other build* methods.

   * Builds an NFT transfer transaction without signing it.

[Copilot]

The buildBridgeRequest method signature declares a return type of Transaction but actually returns { ...tx, intent }, which includes the extra intent field. Update the return type to include intent (e.g., a union or extended interface) or remove the extra property to match the declared type.

Suggested change

	async buildBridgeRequest({ destination, amount, token_id, intent }: BridgeRequestArgs): Promise<Transaction> {
	async buildBridgeRequest({ destination, amount, token_id, intent }: BridgeRequestArgs): Promise<BridgeTransaction> {

[Copilot]

[nitpick] There are two builder methods for the same CreateDelegationId action (buildDelegate and buildDelegationCreate), which may confuse consumers. Consider consolidating these into a single named builder to reduce duplication.