DataDrivenSR incompatible with SymbolicUtils v4 (needs SymbolicRegression v2 update)

[ChrisRackauckas-Claude]

Problem

DataDrivenSR currently depends on SymbolicRegression = "1" (up to v1.12.0), which only supports SymbolicUtils versions 0.19 through 3.x. The main DataDrivenDiffEq package now requires SymbolicUtils v4, making it impossible to resolve dependencies for DataDrivenSR tests. All DataDrivenSR CI tests and the docs build fail at dependency resolution with:

Unsatisfiable requirements detected for package SymbolicUtils [d1185830]:
  - restricted to versions 4 by project, leaving only versions: 4.0.0 - 4.17.0
  - restricted by compatibility requirements with SymbolicRegression [8254be44]
    to versions: [0.19.0 - 0.19.11, 1.0.5 - 3.32.0] or uninstalled
    -- no versions left

Required Changes

SymbolicRegression v2 supports SymbolicUtils v4, but it is still in alpha (v2.0.0-alpha.9) and has breaking API changes:

1. Options constructor - likely redesigned
2. equation_search keyword arguments - numprocs, procs, parallelism, runtests may have changed
3. calculate_pareto_frontier - may be renamed or have different return types
4. node_to_symbolic - SymbolicUtils extension interface likely changed
5. SymbolicUtils.Sym{LiteralReal} - type constructors may differ in SymbolicUtils v4
6. DynamicExpressions - jumped from v1 to v2

Current Workaround

DataDrivenSR has been removed from the CI test matrix and docs build in #591 until this is resolved.

Action Items

• Wait for SymbolicRegression v2.0.0 stable release
• Update lib/DataDrivenSR/Project.toml compat to SymbolicRegression = "2"
• Update DataDrivenSR source code for v2 API changes
• Re-enable DataDrivenSR in CI matrix (.github/workflows/CI.yml)
• Re-enable DataDrivenSR in docs build (docs/make.jl)