feat: add retry util

[FarajiOranj]

Summary

Closes #136.

Adds a built-in retry utility that calls a function and retries it if it
throws, until it succeeds or a maximum number of attempts is reached. The docs
showed a couple of hand-rolled retry loops; this makes it a first-class helper.

Usage

import { retry } from "@gud/drift";

const hash = await retry(() => drift.write({ abi, address, fn, args }), {
  maxAttempts: 5,
  // Only retry transient errors.
  shouldRetry: (error) => isTransient(error),
});

API

retry(action, options?) calls action(attempt) (1-based) and returns its
result, retrying on throw. Options:

• maxAttempts (default 3) - total attempts, including the first. Values
  less than 1 are treated as 1 (the action always runs at least once).
• delay - the wait before each retry in ms, or a function of the failed
  attempt number. Defaults to an exponential backoff (100ms, 200ms, ...).
• shouldRetry (error, attempt) => boolean | Promise<boolean> - return
  false to rethrow immediately. Defaults to always retrying until
  maxAttempts.

On the final attempt it throws the last error without waiting or consulting
shouldRetry, and a throwing delay strategy never masks the action's error.

Also exports RetryOptions, DEFAULT_MAX_ATTEMPTS, and defaultRetryDelay, and
updates the "Retry Logic" docs to point at the built-in util.

Notes / possible follow-up

The issue also mentions "possibly options on client operations for automatic
retries." I kept this PR to the standalone utility (which composes with any
operation); wiring per-operation retry options into the client would make a good
follow-up.

Tests

retry.test.ts covers success without retry, retry-until-success, throwing the
last error, maxAttempts (incl. <= 1), attempt numbering, the delay strategy,
shouldRetry (false / awaited / not-called-on-final), and that a throwing delay
strategy rethrows the original error.

[changeset-bot]

🦋 Changeset detected

Latest commit: d3a1d98

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 5 packages

Name	Type
@gud/drift	Minor
@gud/drift-ethers-v5	Minor
@gud/drift-ethers	Minor
@gud/drift-viem	Minor
@gud/drift-web3	Minor

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