fix(key-wallet): extend gap limit for operator keys like owner/voting keys

[QuantumExplorer]

Problem

When a ProRegTx/ProUpRegTx marks a provider key as used, wallet_checker runs maintain_gap_limit on the matched account's pools — but it obtained the derivation key via extended_public_key_for_account_type, which returns None for BLS accounts ("These use BLS/EdDSA keys, not regular xpubs"), so the loop continued before gap maintenance. Result: owner and voting pools extend past used keys, the operator pool never does. A wallet whose pre-generated operator keys were all consumed by registrations would stop detecting registrations made with its next operator keys.

All the machinery below the checker already supported this: KeySource::BLSPublic does legacy-scheme non-hardened derivation (the same path used to pre-generate the pool), and the operator pool is AddressPoolType::Absent (non-hardened), so watch-side extension is possible.

Changes

• Wallet::key_source_for_account_type (new, in wallet/helper.rs): key-source counterpart of extended_public_key_for_account_type. ECDSA accounts yield KeySource::Public; the provider operator account yields KeySource::BLSPublic from its stored account xpub; account types that cannot derive publicly yield NoKeySource.
• wallet_checker: gap maintenance now sources its key through the new helper and only skips on NoKeySource, so operator pools extend exactly like owner/voting pools.
• Platform-node (EdDSA) pools remain excluded — SLIP-0010 supports hardened derivation only, so extending them requires the seed, which the checker doesn't (and shouldn't) hold. This is now documented on the helper rather than implicit in a None.

Tests

provider_registration_extends_operator_key_gap_limit: derives operator key 0, processes a ProRegTx carrying it, and asserts the pool extends to highest_used + gap_limit, with the freshly derived entries surfaced in new_addresses and their BLS public keys matching the audited operator_public_key_at entry point (#880/#881). Verified the test fails without the source change (pool stays at the pre-generated window, Some(4) != Some(5)).

Full cargo test -p key-wallet --all-features (544 passed), clippy -D warnings, and fmt are clean; key-wallet-ffi, key-wallet-manager, and dash-spv still compile.

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📥 Commits

Reviewing files that changed from the base of the PR and between bc6cbf9 and b52200e.

📒 Files selected for processing (3)

• key-wallet/src/tests/special_transaction_matching_tests.rs
• key-wallet/src/transaction_checking/wallet_checker.rs
• key-wallet/src/wallet/helper.rs

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch claude/operator-gap-limit

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.28%. Comparing base (bc6cbf9) to head (b52200e).

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #882      +/-   ##
==========================================
+ Coverage   74.23%   74.28%   +0.04%     
==========================================
  Files         326      326              
  Lines       74585    74602      +17     
==========================================
+ Hits        55370    55415      +45     
+ Misses      19215    19187      -28     

Flag	Coverage Δ
core	77.09% <ø> (ø)
ffi	50.31% <ø> (ø)
rpc	20.00% <ø> (ø)
spv	91.08% <ø> (+0.14%)	⬆️
wallet	74.32% <100.00%> (+0.03%)	⬆️

Files with missing lines	Coverage Δ
...-wallet/src/transaction_checking/wallet_checker.rs	99.24% <ø> (ø)
key-wallet/src/wallet/helper.rs	67.68% <100.00%> (+1.76%)	⬆️

... and 7 files with indirect coverage changes