chore: update the chain follower logs to report validation

[akaladarshi]

Summary of changes

Changes introduced in this pull request:

• Instead of the max forks epoch remaining to start validation, now log shows min epochs remaining to start validation
• Update the chain follower logs to report the remaining tipset to start validation instead of remaining downloads

Reference issue to close (if applicable)

Closes #5499

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

• This pull request is based on an issue that a maintainer has accepted (see Before Opening a Pull Request).
• 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

• Bug Fixes
  • Improved chain synchronization progress reporting while catching up to the latest chain head.
  • Status messages now provide clearer stage-based information, including validation progress.
  • Progress updates are shown only when synchronization is significantly behind, reducing unnecessary log noise.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: c1a644d5-e76c-417b-bda4-dda82e3f0f0f

📥 Commits

Reviewing files that changed from the base of the PR and between d44ecc7 and 9cb988c.

📒 Files selected for processing (1)

• src/chain_sync/chain_follower.rs

🔗 Linked repositories identified

CodeRabbit considers these linked repositories for cross-repo context during reviews:

• filecoin-project/lotus (manual)

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Walkthrough

ChainFollower catch-up progress logging now uses the epoch gap to HEAD and reports fork validation stages instead of the number of queued tipsets.

Changes

Catch-up progress reporting

Layer / File(s)	Summary
Epoch-based fork status logging src/chain_sync/chain_follower.rs	Progress logs are emitted only when the expected-head and heaviest-chain epochs differ by more than 10, with status text describing pending or active fork tipset validation.

Estimated code review effort: 3 (Moderate) | ~15 minutes

Possibly related PRs

• ChainSafe/forest#7179: Changes task lifecycle and cleanup semantics used by fork state handling.
• ChainSafe/forest#7380: Also updates chain_follower.rs catch-up progress logging based on epoch distance.

Suggested reviewers: hanabi1224

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title matches the main change: updating ChainFollower logs to report validation progress.
Linked Issues check	✅ Passed	The updated catch-up logging reports epochs remaining before validation and is independent of fork count, matching #5499.
Out of Scope Changes check	✅ Passed	The diff stays focused on ChainFollower catch-up logging and adds no unrelated behavior.

✨ 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 akaladarshi/sync-log-validation-start

✨ Simplify code

• Create PR with simplified code
• Commit simplified code in branch akaladarshi/sync-log-validation-start

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 65.06%. Comparing base (a6f303b) to head (9cb988c).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/chain_sync/chain_follower.rs	0.00%	22 Missing ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
src/chain_sync/chain_follower.rs	30.76% <0.00%> (-0.19%)	⬇️

... and 4 files with indirect coverage changes

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