feat(bitcoin): add headless + browser wallet SDK

[jinglescode]

Summary

• BitcoinHeadlessWallet — in-process signer: BIP-39 → BIP-32 root → BIP-84 (P2WPKH payment) + BIP-86 (P2TR ordinals). Implements all 7 IBitcoinWallet methods (getNetwork, getAddresses, getAccounts, getBalance, signMessage, signTransfer, signPsbt).
• BitcoinBrowserWallet — registry + Xverse adapter speaking Sats Connect over provider.request(method, params). Handles both the sats-connect-core-normalised {status, result} envelope and the raw JSON-RPC 2.0 {jsonrpc, result} envelope so it works against any Xverse build.
• 93 bitcoin tests across 5 suites — BIP-84/86 mainnet vectors, recoverable-signature round-trip verification (recover pubkey → derive P2WPKH → match address), dust-aware change handling, Taproot tweaked-key signing (BIP-341), Xverse wire-format compatibility, address-type validation.

Crypto correctness

• signMessage produces a 65-byte ECDSA recoverable signature with the "Bitcoin Signed Message:\n" magic prefix and computed recovery id — verifiable by Electrum / Sparrow / bitcoinjs-message.
• signTransfer opts into BIP-125 RBF (sequence 0xfffffffd), uses realistic P2WPKH vbyte math (overhead 11, input 68, output 31), and absorbs sub-dust change (< 546 sats) into the miner fee instead of producing a non-standard output.
• signPsbt for Taproot uses BIP-86 single-key spend with the tweaked private key; signer's publicKey exposes the tweaked output key (matching bitcoinjs-lib's getTaprootHashesForSig check) and tapInternalKey is set on the PSBT input so finalisers can round-trip.

Dependencies (3 added)

• bitcoinjs-lib ^6.1.7
• bip39 ^3.1.0
• ecpair ^2.1.0

(reuses existing bip32 ^5.0.0 + tiny-secp256k1 ^2.2.4)

Test plan

• npx tsc --noEmit — no errors in src/ or test/
• npx jest test/bitcoin/ — 5 suites, 93 tests pass
• npx jest (full repo) — 16 suites, 171 tests pass
• npx tsup — ESM 187 KB + CJS 173 KB + dts 39 KB builds clean
• Manual: connect Xverse on testnet4, fetch balance, send small transfer
• Manual: sign+broadcast PSBT from a third-party builder against testnet4

🤖 Generated with Claude Code

[Temasar1]

feat(bitcoin): harden wallet SDK — provider interfaces, address APIs, verification & cleanup

Provider interfaces (IBitcoinFetcher / IBitcoinSubmitter)

• Added fetchUTxOs(txid, vout?) to IBitcoinFetcher — mirrors Cardano's IFetcher.fetchUTxOs(hash, index?), allowing callers to look up unspent outputs by transaction hash + optional output index. Implemented in both providers using Esplora /tx/{txid} + /tx/{txid}/outspends.

IBitcoinWallet interface & implementations

• Added 5 address/xpub methods to IBitcoinWallet with clear UnsupportedOperation stubs in BitcoinBrowserWallet and XverseAdapter (browser extension wallets don't hold keys):
  • getAddressesByPurpose(purpose) — all derived addresses for a purpose
  • findManagedAddress(address) — reverse lookup of a managed address
  • getAccountXpub(account?) — BIP-84 account xpub (P2WPKH)
  • getTaprootXpub(account?) — BIP-86 account xpub (P2TR)
  • getAccountZpub(account?) — zpub encoding of the BIP-84 xpub

BitcoinHeadlessWallet

• Added fetchUTXOs(purposes?) and getTransactionHistory(options?) for on-chain data access.
• Wired all new IBitcoinWallet methods through to BitcoinAddressManager.
• Updated all internal provider call sites to the renamed method names.
• Removed stray scratch code left at end-of-file that caused Jest suite parse errors.

XverseAdapter

• Added normalizePurpose guard — purpose values from the Xverse response are now validated against the AddressPurpose enum. Unknown values are filtered out silently rather than blindly cast.

Tests

• All 198 tests pass (17 suites).
• Updated verifyMessage assertions across verify-message.test.ts, xverse-adapter.test.ts, and bitcoin-browser-wallet.test.ts to assert on result.valid / result.reason.
• Updated bitcoin-headless-wallet.test.ts mock to match renamed provider methods.
• Added/expanded coverage for XverseAdapter and BitcoinBrowserWallet.

submitted with transaction to verify with bitcoin and headless wallet
https://mempool.space/testnet4/tx/2005d6691167973c76531820eb5867eaccdd494723c2829673ffeb2f3a00f856