fix: gate FilterHeadersSyncComplete on block header sync completion

[xdustinface]

Without this gate, FilterHeadersSyncComplete could fire before BlockHeaderSyncComplete when filter headers caught up to incrementally stored block headers. This caused downstream sync phases (filters, blocks) to start before all headers were available, leading to sync stalls.

Add block_headers_synced flag to FilterHeadersManager that is set only when BlockHeaderSyncComplete is received. Extract try_complete_sync helper to centralize the completion predicate across all four emission points.

Summary by CodeRabbit

Release Notes

• Bug Fixes

  • Refined synchronization completion logic to enforce proper sequencing of operations, ensuring all prerequisites are satisfied before sync completion is confirmed.
  • Added validation to prevent incomplete operations from being incorrectly marked as finished.

• Tests

  • Extended test coverage for synchronization completion with new tests validating edge cases, dependency satisfaction, and proper state transitions.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: e84b2e47-349b-483a-9f32-63684dc2cd7c

📥 Commits

Reviewing files that changed from the base of the PR and between dda1db7 and 26ecb2d.

📒 Files selected for processing (2)

• dash-spv/src/sync/filter_headers/manager.rs
• dash-spv/src/sync/filter_headers/sync_manager.rs

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📝 Walkthrough

Walkthrough

Added a block_headers_synced boolean field to FilterHeadersManager and introduced try_complete_sync() method to gate filter headers sync completion on both block headers sync completion and target height progress. Refactored sync completion logic to use centralized method instead of inline checks.

Changes

Cohort / File(s)	Summary
Synchronization Gate Logic dash-spv/src/sync/filter_headers/manager.rs, dash-spv/src/sync/filter_headers/sync_manager.rs	Added block_headers_synced field to track block header sync completion. Introduced try_complete_sync() method that only emits FilterHeadersSyncComplete when both block_headers_synced is true and progress reaches target height. Refactored both files to delegate sync completion decisions to this centralized method and properly manage the flag based on BlockHeaderSyncComplete events.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐰 Hops in sync with golden code,
Block headers pave the wavy road,
Filter frames now wait their turn,
Till both flags in hearts do burn!
One true gate, no race today,
We hop together, synchronized way! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically describes the main change: adding a gate to FilterHeadersSyncComplete that depends on block header sync completion, which matches the core fix in the changeset.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/filter-headers-sync-ordering

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[codecov]

Codecov Report

❌ Patch coverage is 97.70115% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.76%. Comparing base (dda1db7) to head (26ecb2d).
⚠️ Report is 2 commits behind head on v0.42-dev.

Files with missing lines	Patch %	Lines
dash-spv/src/sync/filter_headers/manager.rs	97.67%	2 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##           v0.42-dev     #631      +/-   ##
=============================================
+ Coverage      67.57%   67.76%   +0.18%     
=============================================
  Files            318      318              
  Lines          67830    67896      +66     
=============================================
+ Hits           45835    46007     +172     
+ Misses         21995    21889     -106     

Flag	Coverage Δ
core	75.21% <ø> (ø)
ffi	38.42% <ø> (+0.86%)	⬆️
rpc	19.92% <ø> (ø)
spv	84.94% <97.70%> (+0.18%)	⬆️
wallet	67.57% <ø> (ø)

Files with missing lines	Coverage Δ
dash-spv/src/sync/filter_headers/sync_manager.rs	100.00% <100.00%> (ø)
dash-spv/src/sync/filter_headers/manager.rs	90.70% <97.67%> (+11.20%)	⬆️

... and 15 files with indirect coverage changes