ListKeys returns keys in wrong order for wallets with 10 or more addresses

[Dunsin-cyber]

When a user has generated 10 or more addresses, ListKeys returns them in the wrong order. This is because the code sorts the keys as text (like words in a dictionary) rather than as numbers. In text sorting, "10" comes before "2"... the same way "cat" comes before "dog" because it only looks at the first character.

go-sdk/wallet/hdwallet/wallet.go

Lines 304 to 306 in 6ce96d1

	sort.SliceStable(keys, func(i, j int) bool {
	return keys[i].Id < keys[j].Id
	})

This doesn't affect users with fewer than 10 addresses because single digit numbers sort the same way whether you treat them as text or numbers.

[arkanaai]

Codebase Context

Root cause confirmed in wallet/hdwallet/wallet.go, ListKeys function (line 304–306):

```go
sort.SliceStable(keys, func(i, j int) bool {
return keys[i].Id < keys[j].Id // lexicographic string compare
})
```

Key IDs are derivation paths formatted as m/0/<index> (see key_service.go:140). String comparison sorts "m/0/10" before "m/0/2", so the order breaks at index 10.

The test in wallet_test.go (TestListKeys) doesn't catch this because it only validates ascending lexicographic order.

---

Acceptance Criteria

• ListKeys returns keys sorted by their numeric derivation index, not lexicographically
• A wallet with ≥10 addresses returns keys in order m/0/0, m/0/1, ..., m/0/9, m/0/10, ...
• Existing test extended (or new test added) that generates ≥10 keys and asserts correct numeric ordering

---

Suggested Fix

Extract the trailing index from the derivation path and compare as integers:

```go
sort.SliceStable(keys, func(i, j int) bool {
indexI := derivationIndex(keys[i].Id)
indexJ := derivationIndex(keys[j].Id)
return indexI < indexJ
})

// helper
func derivationIndex(id string) int {
parts := strings.Split(id, "/")
idx, _ := strconv.Atoi(parts[len(parts)-1])
return idx
}
```

Alternatively, zero-pad indices at creation time (m/0/%010d) — but that's a larger, breaking change to the ID format and not recommended.