fix(consensus/XDPoS,core): fix verifyheaders parent lookups for epoch switches

[gzliudan]

Proposed changes

Problem: VerifyHeaders could fail on epoch-switch batches when consensus hooks looked up parent headers through ChainReader before the batch had been written to disk.

Cause: the import paths passed the raw chain reader into VerifyHeaders, so helper lookups could only see DB-backed state and missed in-flight headers during block and header-only imports.

Solution: wrap the VerifyHeaders entry points with a batch-aware verifyChainReader so current-batch headers and blocks are visible during validation, add focused regression tests for epoch-switch parent resolution, and keep wrapper reuse as a no-op instead of mutating an existing cache.

Fix: XinFinOrg/XinFin-Node#258

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• build: Changes that affect the build system or external dependencies
• ci: Changes to CI configuration files and scripts
• chore: Changes that don't change source code or tests
• docs: Documentation only changes
• feat: A new feature
• fix: A bug fix
• perf: A code change that improves performance
• refactor: A code change that neither fixes a bug nor adds a feature
• revert: Revert something
• style: Changes that do not affect the meaning of the code
• test: Adding missing tests or correcting existing tests

Impacted Components

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• Consensus
• Account
• Network
• Geth
• Smart Contract
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Checklist

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• This PR has sufficient test coverage (unit/integration test) OR I have provided reason in the PR description for not having test coverage
• Tested on a private network from the genesis block and monitored the chain operating correctly for multiple epochs.
• Provide an end-to-end test plan in the PR description on how to manually test it on the devnet/testnet.
• Tested the backwards compatibility.
• Tested with XDC nodes running this version co-exist with those running the previous version.
• Relevant documentation has been updated as part of this PR
• N/A

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[Copilot]

Pull request overview

Fixes XDPoS header batch verification during epoch switches by ensuring consensus parent/header lookups can see in-flight (not-yet-persisted) headers/blocks during VerifyHeaders, preventing false unknown ancestor-style failures during imports.

Changes:

• Introduces a batch-aware consensus.ChainReader wrapper (verifyChainReader) that shadows header/block lookups with current-batch entries.
• Updates block and header-only import paths to pass a batch-aware reader into VerifyHeaders for XDPoS.
• Adds regression tests covering epoch-switch parent resolution during VerifyHeaders and InsertHeaderChain.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
core/headerchain.go	Wraps VerifyHeaders calls with a batch-aware reader for XDPoS during header-chain validation.
core/blockchain.go	Wraps VerifyHeaders calls with a batch-aware reader (including blocks) for XDPoS during block insertion.
consensus/XDPoS/XDPoS.go	Ensures XDPoS VerifyHeaders uses a batch-aware reader so helper lookups can see in-batch headers.
consensus/XDPoS/verify_chain_reader.go	Adds verifyChainReader implementation to shadow header/block lookups with batch data.
consensus/XDPoS/verify_chain_reader_test.go	Adds unit tests validating wrapper behavior (nil-safety, shadowing, reuse semantics).
consensus/tests/engine_v2_tests/verify_chain_reader_test.go	Adds focused regression tests for epoch-switch parent resolution in VerifyHeaders and header-only import.

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