Remove Colt dependency, replace with commons-math4-legacy

[alexeid]

Summary

• Replace vendored colt.jar with commons-math4-legacy (already a dependency), removing a dependency rather than adding one
• Unblocks publishing beast3 to Maven Central (colt.jar was a local jar not on Central)
• Mark beagle as optional so it does not block Maven Central consumers
• Add Maven Central release job to CI workflow (triggered by v* tags)

Changes

File	Change
RobustEigenDecomposition	Accept/return double[][] instead of Colt matrix types; inline symmetry check
RobustSingularValueDecomposition	Accept/return double[][] instead of Colt matrix types
ColtEigenSystem	Use LUDecomposition from commons-math4 for matrix inverse
ComplexColtEigenSystem	Adapt to new return types
KernelDensityEstimator2D	Replace DoubleArrayList/Descriptive.quantile() with sorted-array quantile
BinaryCovarionModelTest	cern.colt.Arrays to java.util.Arrays
module-info.java (both)	Remove requires colt
pom.xml (both)	Remove colt dep, mark beagle optional
ci-publish.yml	Remove colt steps, add Maven Central release on v* tags

Test plan

• mvn verify passes (all tests green, zero failures)
• Manual testing of substitution models that use ColtEigenSystem (e.g. GTR, HKY, BinaryCovarion)
• Manual testing of ComplexColtEigenSystem path (non-reversible models)
• Manual testing of KernelDensityEstimator2D (TreeAnnotator HPD contours)

Closes #44