QA: run_qa v1.6 form + ExplicitImports

[ChrisRackauckas-Claude]

Please ignore until reviewed by @ChrisRackauckas.

Converts test/qa/qa.jl from the hand-rolled Aqua/JET/ExplicitImports body to the SciMLTesting v1.6 run_qa form with explicit_imports = true (all 6 ExplicitImports checks now run).

ExplicitImports findings

Check	Result
no_implicit_imports	pass (no change)
no_stale_explicit_imports	pass (no change)
all_explicit_imports_via_owners	pass (no change)
all_explicit_imports_are_public	pass (no change)
all_qualified_accesses_via_owners	FIXED in source
all_qualified_accesses_are_public	IGNORE (2 Random stdlib internals)

FIX (all_qualified_accesses_via_owners): rand/randn are owned by Base and only re-exported by Random, so the PassthroughRNG methods are now defined as Base.rand/Base.randn instead of Random.rand/Random.randn. Random.randexp / Random.rng_native_52 / Random.default_rng are genuinely Random-owned and unchanged.

IGNORE (all_qualified_accesses_are_public): default_rng and rng_native_52 are Random stdlib internals (not public in Random): default_rng is the standard default-RNG accessor; rng_native_52 is extended for the PassthroughRNG sampler chain. There is no way to make a stdlib's own non-public names public, so these are ignored via ei_kwargs with the source documented in a comment.

No @test_broken markers were needed (none existed previously; 0 hard fails after the fix + ignore).

Deps (test/qa/Project.toml)

• SciMLTesting compat bumped to "1.6".
• Dropped ExplicitImports (transitive via SciMLTesting) and Random (qa.jl no longer uses it).
• Kept Aqua (the ambiguities sub-check spawns a child process that needs Aqua a direct dep), JET (JET runs), SafeTestsets (the run_tests @safetestset wrapper must be able to load it in the QA env), and Test.

Verification (vs released SciMLTesting 1.6.0, no dev-from-branch)

• QA group: 18/18 pass on Julia 1.10 (lts) and 1.12 (release), 0 Fail/Broken/Error.
• Core group: passes on Julia 1.10 (confirms the Base.rand/Base.randn source change is behavior-preserving).

🤖 Generated with Claude Code