fix: Skip deleted book directories and non-root modifications in ValidBookDirectory invariant

[PeterChen13579]

High Level Overview of Change

Update ValidBookDirectory to validate newly-created directory nodes and modified
directory nodes only when sfRootIndex changes. This keeps legacy bad
exchange-rate metadata from causing false positives during ordinary
modifications, while still checking root-link changes.

Context of Change

API Impact

• Public API: New feature (new methods and/or new fields)
• Public API: Breaking change (in general, breaking changes should only impact the next api_version)
• libxrpl change (any change that may affect libxrpl or dependents of libxrpl)
• Peer protocol change (must be backward compatible or bump the peer protocol version)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.3%. Comparing base (30de556) to head (da9d9c4).

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #7312   +/-   ##
=======================================
  Coverage     82.3%   82.3%           
=======================================
  Files         1011    1011           
  Lines        76303   76305    +2     
  Branches      7314    7312    -2     
=======================================
+ Hits         62827   62836    +9     
+ Misses       13476   13469    -7     

Files with missing lines	Coverage Δ
src/libxrpl/tx/invariants/DirectoryInvariant.cpp	100.0% <100.0%> (ø)

... and 5 files with indirect coverage changes

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[Copilot]

Pull request overview

This PR updates the ValidBookDirectory invariant to ignore deleted directory entries, preventing legacy/bad book-root directories that are being removed from being misclassified as newly-created bad state. It also adds a regression test covering the deletion callback scenario where the deleted SLE image may still be provided to the invariant.

Changes:

• Update ValidBookDirectory::visitEntry to early-return when isDelete is true.
• Add a unit/regression test ensuring deleting a legacy bad root directory does not trip the invariant.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/libxrpl/tx/invariants/DirectoryInvariant.cpp	Skips invariant checks for deleted entries via the isDelete marker to avoid false positives.
src/test/app/Invariants_test.cpp	Adds regression coverage for deletion of a legacy bad root book directory where the deleted SLE image is still passed to visitEntry.

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[ximinez]

🐒 🔧

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

[PeterChen13579]

/ai-review

[xrplf-ai-reviewer]

No issues.

Review by Claude Opus 4.6 · Prompt: V15

[ximinez]

My issues are addressed.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.