QA: run_qa v1.6 form + ExplicitImports (#59)

Convert the hand-rolled `test/qa/qa.jl` (direct `Aqua.test_all` +
`JET.test_package`) onto the SciMLTesting v1.6 `run_qa` form and enable
the ExplicitImports checks:

    using SciMLTesting, FastPower, JET, Test
    run_qa(FastPower; explicit_imports = true)

Aqua, JET, and all six ExplicitImports checks pass cleanly (FastPower has
no external `[deps]`, so EI is trivially clean — no ignore-lists, no broken
markers needed).

The previous `@test_broken` placeholder for the Aqua `deps_compat` extras
finding (#53) is dropped: that finding was the `Pkg` extra missing a compat
entry, and `Pkg` was already removed from the root `[extras]`/test target in
#54. Verified against released SciMLTesting 1.6.0 that the full default
`Aqua.test_all(FastPower)` now passes the deps_compat (extras) sub-check, so
the marker was stale — issue #53 can be closed.

test/qa/Project.toml: bump SciMLTesting compat to "1.6"; drop the explicit
`check_extras = false` tweak (no longer needed). ExplicitImports stays a
transitive dep via SciMLTesting (not listed directly); Aqua kept as a direct
dep (its ambiguities sub-check child-procs), JET and SafeTestsets kept.

Verified locally (clean depot, released SciMLTesting 1.6.0, GROUP=QA via
run_tests folder-model): Quality Assurance 18/18 Pass, 0 Fail/Error/Broken.

Co-authored-by: ChrisRackauckas-Claude <accounts@chrisrackauckas.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: 3 people

test/qa/Project.toml

@@ -13,6 +13,6 @@ FastPower = {path = "../.."}
 Aqua = "0.8"
 JET = "0.9,0.10,0.11"
 SafeTestsets = "0.1, 1"
-SciMLTesting = "1"
+SciMLTesting = "1.6"
 Test = "1"
 julia = "1.10"

test/qa/qa.jl

@@ -1,13 +1,3 @@
-using FastPower
-using Aqua
-using JET
-using Test
+using SciMLTesting, FastPower, JET, Test
 
-@testset "Aqua" begin
-    Aqua.test_all(FastPower; deps_compat = (; check_extras = false))
-    @test_broken false  # Aqua deps_compat (extras): Pkg has no [compat] entry — see https://github.com/SciML/FastPower.jl/issues/53
-end
-
-@testset "JET" begin
-    JET.test_package(FastPower; target_defined_modules = true)
-end
+run_qa(FastPower; explicit_imports = true)