feat(wallet): complete derived-account lifecycle parity

[ben-kaufman]

Summary

• Load derived on-chain accounts from Config::onchain_wallet_accounts after validating each account index and xpub against the node seed.
• Add runtime account removal that retains account-specific BDK state and safely ignores sync results that arrive after unload.
• Add account-specific address metadata lookup by index and contiguous range.
• Make Electrum full-scan batch size and stop gap configurable for non-primary wallets, with Bitkit-compatible values of 100 and 1000.
• Bump the Synonym fork to 0.7.0-rc.55 and regenerate Swift, Android Kotlin, JVM Kotlin, Python, and native binding artifacts.

Behavior

Runtime add/remove changes are not persisted as registration state. Applications can persist { address_type, account_index, xpub } in their own configuration and supply it through Config::onchain_wallet_accounts on every build. Removing an account only unloads it from the aggregate wallet; re-adding it recovers the existing account-specific BDK namespace.

Account 0 remains reserved for the configured primary and monitored address-type wallets. Derived accounts cannot become the receive/change wallet.

ElectrumSyncConfig::additional_wallet_full_scan_batch_size and additional_wallet_full_scan_stop_gap apply only to monitored/derived wallets during full scans. Defaults remain 5 and 20; primary-wallet full scans and all incremental syncs retain their existing behavior.

Esplora and Electrum can recover confirmed history for newly loaded accounts through full scans. Bitcoind still starts brand-new accounts at the known tip and cannot recover confirmed pre-registration history.

Verification

• cargo fmt --check
• git diff --check origin/main...HEAD
• cargo test --lib (72 passed)
• cargo test --lib --features uniffi (82 passed)
• cargo check --all-targets --all-features
• cargo test --doc (12 passed)
• Config-load/runtime-remove integration test in native and UniFFI modes
• Account index/range lookup integration test in native and UniFFI modes
• Configured-account Electrum restart recovery from externally funded index 30 with batch 100 and stop gap 1000, in native and UniFFI modes
• Full ./bindgen.sh generation and platform builds
• Swift archive checksum verified against Package.swift: 098d48d602fe000f1a9dbc7e758a0fe7bd8720c12b0036c38edf38283edd55f3

Strict cargo clippy --lib -- -D warnings remains blocked by pre-existing lint failures on origin/main; this PR does not add unrelated lint cleanup.

Release

• v0.7.0-rc.55

[chatgpt-codex-connector]

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