Export wallets with BIP 389 multipath descriptors for both receive and change branches

[Copilot]

Wallet exports (PDF, JSON, QR codes) were only including the receive descriptor /0/*, omitting change addresses. Hardware wallets importing these backups could not derive change addresses.

Changes

Export with combined descriptor (wallet.py)

• Changed account_map property to use descriptor.to_string() which returns BIP 389 multipath syntax <0;1>/* instead of just recv_descriptor (/0/*)
• Affects all export paths: PDF backup, JSON export, and QR codes

Backward compatible import (wallet_importer.py)

• Added regex conversion <0;1>/* → 0/* during import to satisfy existing validation logic
• Wallet is created with both branches regardless (internal invariant)

Test coverage (test_wallet.py)

• New test verifies account_map exports combined descriptor with 2 branches

Example

Before:

{"descriptor": "wpkh([fp/84h/0h/0h]xpub.../0/*)#checksum"}

After:

{"descriptor": "wpkh([fp/84h/0h/0h]xpub.../<0;1>/*)#checksum"}

The combined descriptor expands to both receive (/0/*) and change (/1/*) branches when parsed by BIP 389-compliant wallets.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Export JSON/PDF for single/multi signature omit change address branch</issue_title>
<issue_description>Describe the bug
When creating a single/multi signature with ambiguous XPUB (i.e. without branch/output address info), Specter export the wallet with branch/output address for receive only (branch /0/*).

To Reproduce
Example steps to reproduce the behavior:

"Add wallet > Single Signature > Add new device > SeedSigner > Scan QR Code [e0c595c5/84'/0'/0']zpub6qV6TyVkDQsoP6XnSgLJxoH7YunCwUKzPZq3FhccdoQT7uS9w5hDo45tLpRQxr6P3FJnwWaCnYJcZSQiXif5WnPQ5rN2yMRHAE5ZyTzQvre and give device a name > Continue > Create single key wallet > give wallet a name and Create wallet > Save Backup PDF"

The first page of the PDF has the QR Code with descriptor as /0/* without change address info:

{"label": "a name", "blockheight": 481824, "descriptor": "wpkh([669dce62/84h/0h/0h]xpub6Cygb51hbAxuxKQ4hwVV5z6YvhauXbhDexEuA7EoAq9DkejbuF2najEM3YdY2BvC39XYa9nHE3R9QWr2yYgTU58LTNQ7ipFQoj4TszqYVeS/0/*)#w0rtkcqe", "devices": [{"type": "other", "label": "gg"}]}

The second page of the PDF has the text with descriptor as /0/* without change address info:

{"label": "a name", "blockheight": 481824, "descriptor": "wp
kh([669dce62/84h/0h/0h]xpub6Cygb51hbAxuxKQ4hwVV5z6YvhauXbhDe
xEuA7EoAq9DkejbuF2najEM3YdY2BvC39XYa9nHE3R9QWr2yYgTU58LTNQ7i
pFQoj4TszqYVeS/0/*)#w0rtkcqe", "devices": [{"type": "other",
"label": "gg"}]}

The same thing happen if you go to "Settings > Export > Go to export details, descriptor as /0/* in the QR Code and the JSON Data:

{"label": "a name", "blockheight": 481824, "descriptor": "wpkh([669dce62/84h/0h/0h]xpub6Cygb51hbAxuxKQ4hwVV5z6YvhauXbhDexEuA7EoAq9DkejbuF2najEM3YdY2BvC39XYa9nHE3R9QWr2yYgTU58LTNQ7ipFQoj4TszqYVeS/0/*)#w0rtkcqe", "devices": [{"type": "other", "label": "gg"}]}

Expected behavior
It would be fine to return ONLY the [fingerprint/deriv/path]xpub... which would be an XPUB with origin-info rather than a complete descriptor... or since Specter Desktop is returning a descriptor that made some assumptions (script wrapper and checksum) to also assume the change path /<0;1>/* rather than assuming receive path only /0/*.

Screenshots

Desktop (please complete the following information):

• Where is your node running: public
• Where is your specter running: Binaries downloaded from Specter site
• If you're running a binary, which OS: Linux
• Browser N/A
• Specter v2.0.5 - May 30, 2024

Additional context
SeedSigner and Krux exports the ZPUB/XPUB without branch/output address info. Specter-DIY "Master public keys Single key/Multisig" also give values without branch/output address info. But Specter-DIY "Wallets > Default > Settings > Export wallet descriptor" gives values with /0/* with branch/output for receive address only.
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Export JSON/PDF for single/multi signature omit change address branch #2494

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[al-munazzim]

Good fix for including both receive and change branches in exports. A few considerations:

1. BIP 389 compatibility: Verify that target wallets (SeedSigner, Krux, etc.) actually support the <0;1>/* multipath syntax. Some older firmware versions might not parse it correctly.

2. Import regex concern: The conversion <0;1>/* → 0/* in wallet_importer.py:

# What if there are multiple multipath parts in a complex descriptor?
# e.g., multi(2, ../<0;1>/*, .../<0;1>/*)

The current regex might not handle all cases. Worth adding a test for multisig descriptors with multipath.

3. Backward compatibility: Good that imports still work - old exports with /0/* will continue to import fine.

4. Checksum: Does changing from /0/* to /<0;1>/* affect the descriptor checksum? The checksum should be recalculated.

Overall: 👍 Good improvement. Might want to verify hardware wallet compatibility before merging.