Document StochasticDiffEqLevyArea public API

[ChrisRackauckas-Claude]

Important

This PR should be ignored until reviewed by @ChrisRackauckas.

Summary

• add docstrings for the seven undocumented public bindings in StochasticDiffEqLevyArea
• add a Lévy-area manual page that renders the complete public API
• wire the sublibrary into the shared documentation environment and navigation

Root cause

SciMLTesting's public-API documentation check began running for this sublibrary in 12b6996e27ea4ea589a30cd4858cb8ecdd3ef446. The preceding commit d7a66c0fe4342a63de74d898d8ecaf64c8eef199 passes QA 18/18, while 12b6996 fails with the same seven missing docstrings seen on current master: Fourier, FrobeniusL2, MaxL2, Milstein, MronRoe, Wiktorsson, and levyarea.

Those exports originated undocumented when the subpackage was added in fdb6fdd2c66ccae2e807aafdb20890a55ceba080; the newer QA check exposed that latent gap.

Impact

The StochasticDiffEqLevyArea QA lane passes without skips or exceptions, and users get rendered reference documentation for the sublibrary's algorithms, error norms, coefficients, and iterated-integral APIs.

This PR intentionally does not include the separate SpecialFunctions compatibility change.

Validation

Run locally on Julia 1.12.6 from current official master 38f01c5fa5cbe2efd164cd8463b4654e6fb305d1:

• StochasticDiffEqLevyArea QA: 19/19 passed
• StochasticDiffEqLevyArea Core: 60/60 passed
• SciMLTesting docstring + rendered-public-API check: 2/2 passed
• full Documenter build: passed; the generated Lévy-area page contains all seven corrected bindings
• Runic 1.7 check: passed
• git diff --check: passed

Process

1. Reproduced the failure in a fresh detached worktree at official master.
2. Verified the adjacent good/bad commit boundary.
3. Added docstrings and rendered documentation together.
4. Re-ran package QA/Core, the rendered API scan, the full docs build, formatting, and diff checks after rebasing the fix onto the latest master.

[ChrisRackauckas-Claude]

Validation scratchpad for commit 1c309d7881ee08b57d90ae4f6b0a66d38acb8b99:

Clean-master reproduction and boundary

• Current official master reproduced the QA failure with 18 passing checks and one failing public-docstring check.
• Missing bindings were exactly: Fourier, FrobeniusL2, MaxL2, Milstein, MronRoe, Wiktorsson, and levyarea.
• Adjacent boundary:
  • d7a66c0fe4342a63de74d898d8ecaf64c8eef199: QA 18/18 passed with SciMLTesting 1.8.
  • 12b6996e27ea4ea589a30cd4858cb8ecdd3ef446: QA failed with the same seven names after enabling SciMLTesting 2.x docs coverage.

Final branch validation

Run on Julia 1.12.6 after applying the focused patch to official master 38f01c5fa5cbe2efd164cd8463b4654e6fb305d1:

• ODEDIFFEQ_TEST_GROUP=QA with CI-equivalent Pkg.test arguments: 19/19 passed
• ODEDIFFEQ_TEST_GROUP=Core with CI-equivalent Pkg.test arguments: 60/60 passed
• run_api_docs(StochasticDiffEqLevyArea; rendered=true, docs_src=...): 2/2 passed
• Full docs/make.jl Documenter build: exit 0
  • generated stochastic/LevyArea/index.html
  • all seven corrected public bindings are present
  • no missing/undefined @docs warning for those bindings
• Runic 1.7 check on every changed Julia file: exit 0
• git diff --check: exit 0

The Documenter run retains the repository's existing warn-only documentation backlog; this patch does not add a missing/undefined binding warning for the new page.

Base freshness

After PR creation, git fetch upstream master && git log HEAD..upstream/master --oneline returned no commits. No rebase is currently needed.

No SpecialFunctions compatibility changes are included in this PR.

[ChrisRackauckas-Claude]

CI classification after the current runs:

• The lanes relevant to this PR are green: docs, Runic, the root downgrade job, the StochasticDiffEqLevyArea downgrade job, and StochasticDiffEqLevyArea Core on LTS/current/prerelease plus QA.
• The failing GPU job is an exact clean-base match. Both PR job 88344260592 and current-master job 88347281685 fail at dae_tests.jl:467 with the same summary (24 passed, 137 failed, 0 errored, 11 broken; nested DAE group 137 failed, 7 broken).
• The red BDF, NLSolve, and SDIRK downgrade jobs reproduce the current-master MatrixOperator failure; the DiffEqDevTools failure is a runner loss; and the TaylorSeries downgrade failure is the already-classified floor issue handled separately in Constrain TaylorSeries test OrderedCollections compat #3965.
• The remaining red QA jobs are in untouched sibling sublibraries and report pre-existing public-API / ExplicitImports debt. The same-base-SHA master sublibrary run is still waiting on runners, so I am classifying those as branch-unrelated by scope, not claiming an exact master comparison.

The overall Sublibrary CI workflow is still pending because one job remains queued, so this is not a claim that all repository CI is green.