wallet_importer: "new range must include current range" on wallet re-create after partial import

[k9ert]

Split from #2335 (see @alvistar and @ironrai comments there).

Symptom

Re-creating a wallet in Specter fails with:

ERROR in wallet_importer: new range must include current range = [0,1008] and new range must include current range = [0,1000]
Traceback (most recent call last):
  File ".../cryptoadvance/specter/util/wallet_importer.py", line 235, in create_wallet
    self.wallet = wallet_manager.create_wallet(...)
  File ".../cryptoadvance/specter/managers/wallet_manager.py", line 353, in create_wallet
    w = self.WalletClass.create(...)
  File ".../cryptoadvance/specter/wallet/wallet.py", line 362, in create
    raise SpecterError(all_issues)
SpecterError: new range must include current range = [0,1001] and new range must include current range = [0,1000]

Reported on v2.0.2 (macOS and Linux). Not verified on current v2.1.7 — please confirm if still reproducible.

Repro (from @ironrai in #2335)

1. Open a wallet, start a transaction, close the dialog without signing.
2. Hit the check_utxo IndexError from Error: Failed to load utxos, IndexError: list index out of range ✕ #2335 and can no longer open the wallet.
3. Try to re-import the wallet under the same name → fails with the error above. Workaround was deleting the wallet file in Bitcoin Core and re-importing under a different name.

Root cause (best guess)

Wallet creation path at `wallet.py:353-362`:

```python
if use_descriptors:
res = wallet_rpc.importdescriptors(args)
else:
res = wallet_rpc.importmulti(args, {"rescan": False})

if not all([r["success"] for r in res]):
all_issues = " and ".join(...)
raise SpecterError(all_issues)
```

On the legacy (non-descriptor) path, args carry `"range": [0, cls.GAP_LIMIT]`. If the Bitcoin Core wallet file already contains the same descriptor at a wider range (e.g. `[0, 1008]` after `keypoolrefill` extended it), Core rejects `importmulti` with a new range of `[0, 1000]` because the new range does not include the current one. Core's rule: range can only grow on re-import, never shrink.

The error only surfaced because the earlier #2335 crash left the Core-side wallet in a state that Specter then couldn't cleanly recover from — but the shrink-refusal is an independent Specter bug.

Suggested fix directions

• Query current descriptor range before re-import and pass `max(current_range_end, GAP_LIMIT)` rather than a fixed `GAP_LIMIT`.
• Or: prefer the descriptor path (`importdescriptors` with `active=True`) for all Core versions that support it — the descriptor path doesn't carry the `range` constraint.
• Or: on shrink-refusal, retry with the wider range extracted from the error, or explicitly re-unload/re-load the wallet file.