Tracking: DynamicQuantities × SciML (DiffEq) compatibility rollout

## Summary

Tracking issue for the DynamicQuantities × SciML (DiffEq stack) compatibility rollout.

Goal: land a minimal, semantically-correct patch stack across repos to support unitful ODE workflows with DynamicQuantities without type-level `zero(::Type{Quantity})` assumptions.

Primary staging reference:
- Bundle PR: https://github.com/MilesCranmerBot/dqdeq-units-bundle/pull/1

---

## Rollout plan (2 waves)

### Wave 1 (root dependency)
- [x] DynamicQuantities.jl PR merged
- [x] DynamicQuantities.jl release/tag published (release process started; tag pending)

### Wave 2 (open downstream PRs in parallel after DQ release)
- [x] DiffEqBase.jl PR
- [x] OrdinaryDiffEqCore.jl PR
- [x] OrdinaryDiffEqDifferentiation.jl PR
- [ ] (optional) ArrayInterface.jl PR
- [ ] (optional) DifferentiationInterface.jl PR

---

## Dependency graph

```mermaid
graph TD
DQ[DynamicQuantities.jl] --> DB[DiffEqBase.jl]
DQ --> ODEC[OrdinaryDiffEqCore.jl]
DQ --> ODED[OrdinaryDiffEqDifferentiation.jl]
DB --> ODED
DQ --> AI[ArrayInterface.jl]
DQ --> DI[DifferentiationInterface.jl]
```

---

## Notes / constraints

- No CI-hack edits in upstream repos just to force green.
- Keep semantic behavior aligned with Unitful/SciML expectations.
- SciML hooks (`value`, `unitfulvalue`) for DQ types should be owned by DynamicQuantities via extension (not downstream piracy).
- Prefer minimal per-repo diffs with explicit dependency links in each downstream PR body.

---

## PR links

- DynamicQuantities.jl: https://github.com/JuliaPhysics/DynamicQuantities.jl/pull/201
- DiffEqBase.jl: https://github.com/SciML/DiffEqBase.jl/pull/1293
- OrdinaryDiffEqCore.jl: https://github.com/SciML/OrdinaryDiffEq.jl/pull/3126
- OrdinaryDiffEqDifferentiation.jl: https://github.com/SciML/OrdinaryDiffEq.jl/pull/3126
- ArrayInterface.jl (optional): _TBD_
- DifferentiationInterface.jl (optional): _TBD_