Add e2e test for joining node with corrupted (truncated) ledger file

[Copilot]

• Understand the issue (cchost crashes in case a corrupt ledger file is found on a node that is joining the network #6612): node crashes when joining with corrupted ledger files
• Explore existing test infrastructure (reconfiguration.py, recovery.py corruption patterns)
• Add test_add_node_with_corrupted_ledger test to tests/reconfiguration.py
• Add the test to the reconfiguration test suite in tests/suite/test_suite.py
• Replace silent skips with assertions when unable to find chunks to corrupt
• Run code review and CodeQL security check (no alerts)

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