Consolidate backlog and reports into README; remove redundant markdown files

[rad1092]

Motivation

• Reduce markdown sprawl and keep the project status/backlog in a single canonical location (README.md).
• Make remaining work (UI, file-format, analysis, performance, architecture) visible and prioritized in-place for quicker triage.
• Adjust the public completion estimate to reflect the consolidated assessment.

Description

• Updated README.md 0) 현재 완성도 빠른 진단 to lower the completion estimate from 92% to 88% and added a prioritized remaining-tasks list (P1–P3) covering UI improvements, analysis quality, structure, performance, and input/file-format expansion.
• Consolidated backlog/report content into the README and removed two redundant files: NEXT_STEPS_UI_AND_BACKLOG.md and REVIEW_REPORT.md.
• Applied the content replacement and cleanup via small automation (inline Python edits) and created a commit consolidating these changes.

Testing

• Verified markdown files before/after with rg --files -g '*.md' and inspected the edited README with nl -ba README.md, both succeeded.
• Removed the two redundant files programmatically with a Python unlink script and confirmed the deletions via git status --short.
• Committed the consolidated changes with git add and git commit, and the commit completed successfully.

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Codex Task