fix: unify logic of getting finalized tipset

[hanabi1224]

Summary of changes

Changes introduced in this pull request:

Reference issue to close (if applicable)

Closes #6792

Other information and links

Change checklist

• I have performed a self-review of my own code,
• I have made corresponding changes to the documentation. All new code adheres to the team's documentation standards,
• I have added tests that prove my fix is effective or that my feature works (if possible),
• I have made sure the CHANGELOG is up-to-date. All user-facing changes should be reflected in this document.

Outside contributions

• I have read and agree to the CONTRIBUTING document.
• I have read and agree to the AI Policy document. I understand that failure to comply with the guidelines will lead to rejection of the pull request.

Summary by CodeRabbit

• Refactor
  • Simplified the internal process for retrieving finalized chain state information by consolidating finality selection logic, reducing code complexity and improving maintainability.

[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 4c8069c5-3039-4e94-839f-85d21184ce5a

📥 Commits

Reviewing files that changed from the base of the PR and between f34ffd1 and a6cee81.

📒 Files selected for processing (1)

• src/rpc/methods/chain.rs

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Walkthrough

The ChainGetFinalizedTipset RPC handler is simplified to delegate finalized tipset resolution to ChainGetTipSetV2::get_latest_finalized_tipset, removing separate F3-fallback logic and eliminating the get_f3_finality_tipset helper function to unify finality resolution across both RPC endpoints.

Changes

Cohort / File(s)	Summary
ChainGetFinalizedTipset Handler Simplification src/rpc/methods/chain.rs	Removed EC finality epoch computation and F3→EC fallback logic from ChainGetFinalizedTipset::handle, replacing it with a direct delegation to ChainGetTipSetV2::get_latest_finalized_tipset. Deleted the private get_f3_finality_tipset helper function that previously fetched F3 certificates and validated finality compatibility.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• fix: track F3 finalized tipset in chain store #6780: Introduces the shared ChainGetTipSetV2::get_latest_finalized_tipset helper that this PR now delegates to for unified finality resolution.
• fix(rpc): avoid unecessarily cloning Tipset #6227: Previously modified the same get_f3_finality_tipset helper function that this PR removes.
• fix(rpc): make ChainGetTipset v2 work with lotus-gateway #6553: Modifies ChainGetTipSetV2 behavior to ensure consistency with the finality selection logic now delegated from ChainGetFinalizedTipset.

Suggested reviewers

• LesnyRumcajs
• akaladarshi
• sudo-shashank

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title 'fix: unify logic of getting finalized tipset' directly and accurately describes the main change: consolidating finalized tipset retrieval logic across RPC methods.
Linked Issues check	✅ Passed	The PR successfully implements the proposed fix from issue #6792 by routing ChainGetFinalizedTipset through ChainGetTipSetV2::get_latest_finalized_tipset, unifying finalized tipset resolution logic and removing divergent F3 fallback logic.
Out of Scope Changes check	✅ Passed	All changes are scoped to unifying finalized tipset logic: the handler delegation and removal of the private get_f3_finality_tipset helper are directly aligned with issue #6792 requirements.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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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 hm/unify-logic-of-get-finalized-tipset

✨ Simplify code

• Create PR with simplified code
• Commit simplified code in branch hm/unify-logic-of-get-finalized-tipset

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@f34ffd1). Learn more about missing BASE report.
⚠️ Report is 3 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/rpc/methods/chain.rs	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
src/rpc/methods/chain.rs	53.18% <0.00%> (ø)

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