feat: migrate DAE failure handling to nlls 2.4 - #7

Summary

• migrate DAE and SDAE algebraic roots to the nlls-gram 2.4 failed-AD contract
• preserve safe inactive-lane inputs while using direct square implicit AD by default
• expose forgiving max_steps_is_success handling and document the JVP-safe initial-point requirement
• prepare tinydiffeq 2.2.0 with the public dependency requirement nlls-gram>=2.4.0

Validation

• uv run ruff check .
• uv run ruff format --check .
• uv run pytest (250 passed, 11 skipped)
• uv run --group docs mkdocs build --strict
• uv build
• uvx twine check dist/tinydiffeq-2.2.0*
• 115-case CPU benchmark suite against published nlls-gram 2.4.0
• 39-case stable AD matrix plus targeted repeat: no sustained JVP/VJP regression crossing