Fix PMD findings from Commons Parent 102

[skrcode]

This follows up #132 and targets the Dependabot branch so the parent upgrade and its required compatibility repair remain one reviewable unit.

What changed

• Move the Pelz-Good accumulators and matrix-power work buffers closer to their first use, satisfying the stricter VariableDeclarationUsageDistance rule without changing their lifetimes.
• Scope the same PMD rule out only for BrentOptimizer.optimize, whose algorithm state must remain alive across loop iterations.

Commons Parent 102 updates the inherited PMD configuration to PMD 7.25.0. The source branch consequently reports eight declaration-distance violations in the inference module; this resolves all eight without weakening the rule globally.

Verification

• mvn -pl commons-statistics-inference -am verify
  • Temurin 17, Maven 3.9.16
  • all five reactor modules passed
  • 49,582 tests passed (48 skipped), with no failures or errors
  • Checkstyle, Apache RAT, SpotBugs, PMD, JaCoCo coverage gates, and japicmp passed
• git diff --check

The final command passed on the exact signed-off patch in an 8 GiB JAIPilot Remote workspace. A preceding 4 GiB run exhausted that workspace's memory while executing the unchanged test/analyzer reactor; no test or analyzer was disabled for the successful run.

Built and verified with JAIPilot:

• Skills: jaipilot-maintainer-intent, jaipilot-fast-execution, jaipilot-review-diff, and jaipilot-remote-java
• Execution profile: gpt-5.6-sol · xhigh · fast