Defer transaction resubmission until scanning completes

[p0mvn]

Summary

• Defer startup and catch-up resubmit_pending_transactions until local scan work is drained, so already-mined wallet txs are not rebroadcast while mined_height is still NULL.
• Harden further by moving the catch-up resubmit pass to after ensure_complete_scan_state, and refusing a tip that advanced on lightwalletd but never landed via update_chain_tip.

Authorship

Original investigation and fix by @ValarDragon in draft #386 (commits authored by Dev Ojha). This PR remakes that work on chainapsis/vizor-wallet and adds a small completion-path hardening follow-up.

Please prefer this PR over #386; the draft can be closed once this lands.

Why

During catch-up (especially with 96-block migration retention batches), Vizor refreshed tip and rebroadcast after each batch before scanning that tip. Resubmit eligibility only checks local mined_height IS NULL, so on-chain txs looked pending and were rebroadcast repeatedly — matching the live pending/Sending-now race analysis.

Tests

• cd rust && cargo test --lib resubmit_: 16 passed

[chatgpt-codex-connector]

💡 Codex Review

vizor-wallet/rust/src/wallet/sync_engine/mod.rs

Lines 2262 to 2263 in 72e4ae7

	let fresh_for_gate = u32::try_from(final_tip_height).unwrap_or(u32::MAX);
	match authoritative_resubmit_tip(final_tip_height, final_tip_height, fresh_for_gate) {

Re-check the chain tip before final resubmit

When the last post-batch tip refresh fails, or it sees a higher lightwalletd tip but update_chain_tip fails, current_tip_height and the DB remain at the old height and the loop can still complete with no pending ranges for that stale tip. This code then fabricates the “fresh” height from final_tip_height, so authoritative_resubmit_tip cannot reject the stale DB tip and resubmit_pending_transactions can rebroadcast a transaction that was already mined or expired in the unobserved new block. Fetch/update the tip here, or carry forward the unsafe refresh state and skip final resubmit unless the DB tip is authoritative.

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