Raise Mooncake compat floor to 0.5.36 (fix Downgrade resolution)

[ChrisRackauckas-Claude]

Raise Mooncake compat floor to 0.5.36 (fix Downgrade resolution)

The root Project.toml declared Mooncake = "0.4.175, 0.5". Mooncake is a
weakdep (backs DataInterpolationsMooncakeExt) that is also a test-target
dependency. julia-actions/julia-downgrade-compat@v2 uses a merged
resolution for old-style [extras]/[targets].test projects and promotes
Mooncake from weakdep to a full dependency, then resolves it at its minimum.
With the old union floor, the downgrade job pins the ancient Mooncake
0.4.175, which is the "promotion-caused Downgrade Unsatisfiable wall".

This narrows the floor to the latest published Mooncake so the downgrade can no
longer select the ancient 0.4.x line.

Change

• Project.toml: Mooncake = "0.4.175, 0.5" -> Mooncake = "0.5.36"
• version bump 9.0.0 -> 9.0.1 (compat narrowing is a patch-level change; a
  Mooncake weakdep floor is not public API)

Old floor raised: Mooncake = "0.4.175, 0.5" -> "0.5.36" (root Project.toml).

Verification (resolves_at_min = true)

Ran julia-actions/julia-downgrade-compat@v2 (the @v2 tip = commit
828d417, i.e. the merged-test-deps path) on this repo on Julia 1.12,
mode=deps, projects=. — identical to the centralized
SciML/.github/.github/workflows/downgrade.yml@v1 invocation this repo uses:

• With the raised floor: resolver installs Mooncake v0.5.36 and reports
  [ Info: Successfully resolved minimal versions for . (with extras). The
  downgraded environment then instantiates and precompiles cleanly
  (DataInterpolations precompiled, INSTANTIATE_OK, exit 0). Mooncake is
  confirmed promoted weakdep -> dependency in the merged project.
• For reference, the original floor resolves to the ancient Mooncake
  0.4.175 — exactly what the raise removes.

So on the current registry snapshot the floor-raise alone yields a clean
downgrade min-resolution; the Resolver-capacity wall (#52) is not hit for
this repo here (resolves_at_min = true).

---

Please ignore until reviewed by @ChrisRackauckas.

[ChrisRackauckas-Claude]

Closing. Verified locally (ran the action's own downgrade.jl on the identical commit CI failed on) that raising the Mooncake compat floor does NOT fix the Downgrade lane. The failure is julia-downgrade-compat@v2 merged mode promoting all ~13 weakdep AD backends (Mooncake, Zygote, ForwardDiff, DifferentiationInterface, …) to hard deps and running Resolver.jl --min on the joint graph — which is registry-snapshot-dependent (flips UNSAT↔SAT as those packages release) and independent of Mooncake's version. This PR also unnecessarily narrows Mooncake compat. Real fix is julia-actions/julia-downgrade-compat#52 (do not promote weakdeps in merged resolution). Superseded — closing.