fix: Change Tuning::bookOffers minimum limit to 1

[bthomee]

High Level Overview of Change

This change updates the rmin of Tuning::bookOffers from 0 to 1.

Context of Change

Although readLimitField now rejects limit == 0 for all callers, Tuning::bookOffers still has rmin = 0. This is inconsistent and makes the tuning misleading.

In particular, the limit value for bookOffers is passed to getBookOffers, and if the limit is 0 the work loop is skipped entirely:

    while (!bDone && iLimit-- > 0)

From both getBookOffers and doBookOffers, there is no other information added to the return, so you'd get an empty JSON result. The correct solution is therefore to change bookOffers minimum to 1, since the value of 0 is rejected anyway as mentioned earlier.

[Copilot]

Pull request overview

Updates RPC tuning to make book_offers’ minimum limit consistent with readLimitField behavior (which rejects limit == 0).

Changes:

• Change RPC::Tuning::bookOffers.rmin from 0 to 1 to avoid misleading tuning configuration.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.5%. Comparing base (dfcad69) to head (f993399).
⚠️ Report is 5 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #6812     +/-   ##
=========================================
- Coverage     81.6%   81.5%   -0.0%     
=========================================
  Files         1011    1010      -1     
  Lines        75979   75982      +3     
  Branches      7634    7652     +18     
=========================================
- Hits         61985   61958     -27     
- Misses       13994   14024     +30     

Files with missing lines	Coverage Δ
src/xrpld/rpc/detail/Tuning.h	100.0% <ø> (ø)

... and 21 files with indirect coverage changes

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