Separate dry-run row operations from projected state

[Widthdom]

Summary

• Add table_row_estimates to dry-run JSON with separate rows deleted, rows inserted/upserted, row operations, projected final rows, and projected row delta.
• Preserve independent value, source, confidence, and unknown reasons for every table/dimension while retaining the legacy mutation fields as explicitly deprecated row-operation aliases.
• Keep human output, CLI help, bilingual documentation, and regression coverage aligned with the new contract.
• Conservatively mark symbol_references dimensions unknown when TypeScript declaration-merging augmentation rebuilds can mutate rows owned by otherwise unchanged files.

Validation

• dotnet build CodeIndex.sln -c Release --no-restore -p:UseSharedCompilation=false (0 warnings, 0 errors)
• Full net8.0 suite: 12,165 passed, 9 skipped, 0 failed (12,174 total)
• Full net9.0 suite: 11,678 passed, 433 skipped, 0 failed (12,111 total)
• Final Release dry-run regression suite on merged main: net8.0 71 passed; net9.0 68 passed, 2 skipped
• Final focused Issue Separate dry-run row-operation estimates from final persisted row counts #5236 fixtures: 2 passed on both net8.0 and net9.0
• dotnet format CodeIndex.sln --verify-no-changes --no-restore
• dotnet run --project tools/CodeIndex.Changelog -- check
• Root index freshness: matched; workspace manifest health: 2/2 healthy

Adversarial review

• Ran two Codex adversarial-review rounds as required by the repository workflow.
• Round 1 found no-op/deletion-only child-table provenance being labeled as parse-derived; corrected it and added regression assertions.
• Round 2 found cross-file TypeScript augmentation cleanup being reported as exact; corrected it with an explicit stable unknown reason and a preview-versus-execution regression fixture.
• All focused and dry-run regression tests passed after the review remediations.

Documentation and changelog

• Updated the English and Japanese sections in README.md, USER_GUIDE.md, DEVELOPER_GUIDE.md, and TESTING_GUIDE.md.
• Added bilingual fragment changelog.d/unreleased/5236.fixed.md.

Follow-up candidates

• None.

Fixes #5236