Enable rendered public API docs QA

[ChrisRackauckas-Claude]

Ignore this PR until reviewed by @ChrisRackauckas.

Summary

• Adds a minimal Documenter docs tree rendering ODEInterfaceDiffEq-owned exported solver APIs.
• Enables SciMLTesting rendered public API docs coverage.
• Ignores DiffEqBase-owned reexports and initialization algorithms reexported from SciMLBase/DiffEqBase for rendered coverage.
• Does not add [sources] or package path source entries.

Validation

• git diff --check: passed.
• Docs build with Julia +1.10: passed; only local Documenter deployment warning.
• Root Pkg.test() with TESTING_GROUP=QA BACKEND_GROUP=CPU: passed the package core suite (algorithm_tests, callbacks, initialization, jac, mass matrix, MTK initialization, saving).
• Direct QA with Julia +1.10: Quality Assurance | 18 pass | 18 total, SciMLTesting v2.2.0 via existing SciMLTesting = "2.1" compat.
• Runic v1.7.0 --check src test docs/make.jl: passed.