fix: secp message gas floor

[LesnyRumcajs]

Summary of changes

Changes introduced in this pull request:

• fix an edge case with under-estimating messages (not applicable right now, but will be once Forest is present as block-producing node)
• tests to ensure eternal compliance and small refactor to a shared MessageChecker

Reference issue to close (if applicable)

Related to #7651 and #7644

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 message validation during block processing.
  • Corrected gas accounting for signed and delegated messages, including signature encoding.
  • Added consistent checks for virtual-machine message inclusion and account sequence ordering.
  • Fixed chain-length calculations to accurately reflect encoded message data and signature types.
  • Improved handling when messages or signatures are modified, ensuring validation and identifiers remain consistent.

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ℹ️ Recent review info

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Configuration used: Repository UI

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📥 Commits

Reviewing files that changed from the base of the PR and between 8da4ad6 and 703295e.

📒 Files selected for processing (1)

• src/chain_sync/tipset_syncer.rs

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• filecoin-project/lotus (manual)

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Walkthrough

The change adds VM-message and chain-length APIs, centralizes BLS and SECP message validation, charges gas from full chain-message encodings, and adds encoding and gas-floor tests. It also changes the memoize dictionary entry.

Changes

Message encoding validation

Layer / File(s)	Summary
Message encoding contract src/message/mod.rs, src/message/signed_message.rs	MessageRead now exposes vm_message() and fallible chain_length(). Implementations account for unsigned, BLS, SECP256K1, and delegated encodings. Tests verify CID and encoding-length consistency, mutations, and signed gas floors.
Shared message checking src/chain_sync/tipset_syncer.rs	MessageChecker validates VM-message inclusion, charges gas from full chain-message encoding, enforces block limits, and tracks sender sequences for BLS and SECP messages. Tests cover SECP signed-encoding gas floors.

Dictionary entry

Layer / File(s)	Summary
Memoize dictionary entry .config/forest.dic	The memoize entry now uses the /D suffix flag.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant TipsetSyncer
  participant MessageChecker
  participant MessageRead
  participant StateTree
  TipsetSyncer->>MessageChecker: Check BLS and SECP messages
  MessageChecker->>MessageRead: Read vm_message and chain_length
  MessageChecker->>StateTree: Validate actors and sequences
  MessageChecker-->>TipsetSyncer: Return validation result

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Merge Risk: ⚪ Minimal · up to 70329

The message gas-floor change has no identified merge-blocking issue.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 58.06% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 31 functions across 4 files.	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 clearly describes the main change: fixing the gas floor for SECP messages.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[codecov]

Codecov Report

❌ Patch coverage is 96.25000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.44%. Comparing base (44f9a53) to head (703295e).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/chain_sync/tipset_syncer.rs	96.84%	0 Missing and 3 partials ⚠️
src/message/signed_message.rs	95.65%	0 Missing and 2 partials ⚠️
src/message/mod.rs	94.73%	0 Missing and 1 partial ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
src/message/mod.rs	92.59% <94.73%> (+0.35%)	⬆️
src/message/signed_message.rs	89.43% <95.65%> (+5.95%)	⬆️
src/chain_sync/tipset_syncer.rs	78.38% <96.84%> (+3.27%)	⬆️

... and 14 files with indirect coverage changes

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[akaladarshi]

@LesnyRumcajs CI is failing

[LesnyRumcajs]

@LesnyRumcajs CI is failing

Not sure who should change - me using British forms of verbs or the CI. I'm tempted to ask AI to do some British Empire encore here. 🤣