refactor(storage): refine recluster levels and log level IO

[zhyass]

I hereby agree to the terms of the CLA available at: https://docs.databend.com/dev/policies/cla/

Summary

• Restrict aggressive recluster mixing to levels 1–3; keep level 0 and each level >= 4 separate, with explicit group ordering before the task budget is consumed.
• Determine promotion from the highest input level's share of uncompressed block bytes: at least 50% advances to max + 1; otherwise keep max. For equal-sized blocks, 1,1,3 -> 3, 1,3,3 -> 4, and 1,2,3 -> 3. Preserve the executor's base-level-plus-one convention.
• Add structured fuse insert output, fuse recluster input, and fuse recluster output logs with table_id, level, block_count, block_size, and file_size. Share ClusterLevelLogStats; preserve per-block insert levels before segment reduction, and exclude unchanged remained blocks from recluster output.
• Consolidate level regression cases and remove redundant tests.

These logs describe selected input and pre-commit write observations, not committed snapshot deltas or complete failed-operation IO accounting. Input levels use the current cluster key's effective statistics; output levels reflect written blocks, including perfect level -1 and NULL for missing cluster statistics. No per-round correlation or new history table is introduced.

Tests

• Unit Test
• Logic Test
• Benchmark Test
• No Test - Explain why

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):

AI assistance

• AI usage: An AI coding assistant helped draft and revise the recluster level calculation, diagnostic logs, regression tests, and PR summary. The responsible human reviewed the diff and directed the simplifications.
• Responsible human: @zhyass
• The responsible human has read every line of this diff and can explain each change

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[chatgpt-codex-connector]

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[zhyass]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. You're on a roll.

Reviewed commit: 5073acad02

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[github-actions]

🤖 CI Job Analysis

Workflow: 34052607323

📊 Summary

• Total Jobs: 32
• Failed Jobs: 3
• Retryable: 0
• Code Issues: 3

❌ NO RETRY NEEDED

All failures appear to be code/test issues requiring manual fixes.

🔍 Job Details

• ❌ mac_check: Not retryable (Code/Test)
• ❌ linux / check: Not retryable (Code/Test)
• ❌ linux / test_unit: Not retryable (Code/Test)

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Automated analysis using job annotations to distinguish infrastructure issues (auto-retried) from code/test issues (manual fixes needed).