Fix SciCompDSL model macro hygiene

[ChrisRackauckas-Claude]

Summary

SciCompDSL's @mtkmodel expansion emitted unqualified names from its own implementation into the caller module. A caller that imported only SciCompDSL therefore failed unless it happened to bind ModelingToolkitBase, Equation, Num, and setmetadata under the expected names.

This captures those owner-module bindings when the macro expands and adds a caller-hygiene regression covering an empty model, equations/defaults, and custom model metadata. No public API is added or changed.

Please ignore this draft until it has been reviewed by @ChrisRackauckas.

Failing before / passing after

I ran the new test against the unfixed source, then restored the source change and ran the identical test:

$ julia +1.12.7 --startup-file=no --project=.validation/root-env -e \
    'using Test; @testset "SciCompDSL macro hygiene" begin include("lib/SciCompDSL/test/macro_hygiene.jl") end'
ERROR: LoadError: UndefVarError: `ModelingToolkitBase` not defined in `Main`

With this commit:

Test Summary:             | Pass  Total
SciCompDSL macro hygiene  |    3      3

The test imports SciCompDSL and selected public ModelingToolkitBase names, but deliberately does not bind the ModelingToolkitBase module name.

Verification

Observed locally with Julia 1.12.7:

SciCompDSL model parsing - MTKBase: 200 passed, 1 pre-existing broken
SciCompDSL model parsing - MTK:     205 passed
SciCompDSL macro hygiene:             3 passed
root QA:                              40 passed
direct SciCompDSL test runner:        passed
Runic check:                          passed
typos:                                passed
git diff --check:                     passed

The full docs build completed the examples and document checks, then failed during final link checking because this unchanged external URL did not answer within the configured 10 seconds:

https://ptolemy.berkeley.edu/projects/embedded/eecsx44/lectures/Spring2013/modelica-dae-part-2.pdf
curl ... --max-time 10
ProcessExited(28)
makedocs encountered an error [:linkcheck]

A retry is running; this change does not touch docs, docstrings, or public API.

Review notes

The interpolated bindings are public/exported from their owning modules. The change does not reach through a re-exporter and does not add a dependency.

🤖 Generated with Claude Code
https://chatgpt.com/codex/tasks/01a03a17-ad6f-7131-82fc-d0fd57ea6512

[ChrisRackauckas-Claude]

A second clean docs build reached CrossReferences and CheckDocument again, then failed only in external link checking:

• the unchanged Berkeley Modelica PDF timed out at curl max-time 10 (ProcessExited(28));
• GitHub rate-limited the unchanged ColPrac README link with HTTP 429.

No doctest, example, cross-reference, or document-check failure was reported before link checking. I am not rerunning the same external network checks a third time.

The failing Optimization CI lanes are the already-reproduced clean-master CasADi 1.3.0 regression, not this SciCompDSL-only diff. The merged CasADi source fix and fully green release draft are at SciML/CasADi.jl#44; current ModelingToolkit master failure evidence is https://github.com/SciML/ModelingToolkit.jl/actions/runs/33444273161/job/99660311800.

I am independently reproducing the downgrade-MTKBase QA lane on the unchanged current master tree before classifying that remaining failure.

https://chatgpt.com/codex/tasks/01a03a17-ad6f-7131-82fc-d0fd57ea6512