Fix docs build: add git [sources] for unregistered QuadDIRECT

[ChrisRackauckas-Claude]

Problem

The Documentation / Build and Deploy Documentation check on master fails at the first instantiate step:

julia --color=yes --project=docs/ -e 'using Pkg; Pkg.develop(PackageSpec(path=pwd())); Pkg.instantiate()'
...
ERROR: expected package `QuadDIRECT [dae52e8d]` to be registered

docs/Project.toml lists both QuadDIRECT and OptimizationQuadDIRECT (which depends on QuadDIRECT) in [deps]. QuadDIRECT is not registered in the General registry and had no [sources] entry, so the docs environment cannot resolve. This reproduces on every recent docs run on master and PRs.

Fix

Add a git [sources] entry for QuadDIRECT pointing at the upstream repository — the same source the QuadDIRECT docs page already instructs users to install manually (] add https://github.com/timholy/QuadDIRECT.jl.git):

[sources.QuadDIRECT]
url = "https://github.com/timholy/QuadDIRECT.jl.git"

Local verification

Ran the exact docs CI command on Julia 1.12 (the docs CI channel):

julia +1.12 --project=docs/ -e 'using Pkg; Pkg.develop(PackageSpec(path=pwd())); Pkg.instantiate()'

Previously this errored at resolution. With the fix, the docs environment resolves and instantiates. The resolved docs/Manifest.toml pulls QuadDIRECT from the git URL and OptimizationQuadDIRECT resolves against it:

[[deps.QuadDIRECT]]
deps = ["LinearAlgebra", "PositiveFactorizations", "StaticArrays"]
repo-rev = "master"
repo-url = "https://github.com/timholy/QuadDIRECT.jl.git"

Scope note

This PR fixes only the docs-build resolution failure. The other current master reds are tracked separately:

• OptimizationCMAEvolutionStrategy [QA] / Julia lts — already fixed by the SciML/.github@v1 develop_sources.jl update (which now skips a dependency's test-only [sources]); that fix landed ~50 min after the stale CI run on master, so this just needs a fresh CI run. Verified locally that the QA group passes 12/12 on Julia 1.10 with the current @v1 script.
• Downgrade / downgrade-sublibraries — the known --min=@alldeps compat-floor conflict on Julia 1.10 (open-ended floors like ComponentArrays >= 0.13.9); a separate, fleet-wide effort.
• ModelingToolkit.jl/All, NeuralPDE.jl/NNPDE downstream — out of scope.

Please ignore until reviewed by @ChrisRackauckas

[ChrisRackauckas-Claude]

Docs build: root-cause analysis + additional fixes pushed

The QuadDIRECT [sources] fix in this PR correctly got the docs build past the Install Dependencies (instantiate) step — verified: on the prior master/PR runs the Documentation job failed at Install Dependencies (the expected package QuadDIRECT to be registered error); on this PR's run that step now passes and the job proceeds to makedocs.

That exposed pre-existing makedocs errors that were previously masked by the early instantiate failure:

ERROR: LoadError: `makedocs` encountered errors [:linkcheck, :example_block] -- terminating build before rendering.

Fixed in commit 22b43d2 (pushed to this branch)

1. :example_block — docs/src/optimization_packages/simpleoptimization.md:25-33
TypeError: in keyword argument linesearch, expected Union{Nothing, LineSearch.AbstractLineSearchAlgorithm}, got a value of type Val{false} at lib/SimpleOptimization/src/SimpleOptimization.jl:223.
   SimpleBFGS/SimpleLBFGS passed the obsolete linesearch = Val(false) to SimpleBroyden/SimpleLimitedMemoryBroyden. SimpleNonlinearSolve v2.x (resolved v2.12.0) types linesearch::Union{Nothing, LineSearch.AbstractLineSearchAlgorithm} and the documented "no line search" value is nothing. Fixed both call sites. This is pre-existing on master and also broke the SimpleOptimization sublibrary's own Core tests (verified: Val(false) -> Core test errors with the identical TypeError; nothing -> Core 7/7 pass on Julia 1.12 / SimpleNonlinearSolve 2.12.0).

2. :linkcheck 404 x4 — docs/src/optimization_packages/evolutionary.md: the four wildart.github.io/Evolutionary.jl/stable/{ga,de,es,cmaes}/ links 404 (Evolutionary.jl moved wildart -> SciML). Repointed to sciml.github.io/Evolutionary.jl/stable/... (all verified 200 via Documenter's exact linkcheck curl) and updated the two github.com/wildart repo links to github.com/SciML (were 301-redirect warnings).

3. :linkcheck timeout x1 — docs/src/optimization_packages/nlopt.md: http://ab-initio.mit.edu/nlopt/ is dead (curl --max-time 10 -> ProcessExited(28)). Repointed to https://nlopt.readthedocs.io/en/latest/ (verified 200).

Remaining blocker — NOT fixable in this repo (upstream SciMLBase)

:linkcheck 403 on https://docs.sciml.ai/Optimization/dev/optimization_packages/optimization. This URL is not a link in Optimization.jl's docs source — it comes from the rendered OptimizationProblem docstring in SciMLBase (src/problems/optimization_problems.jl:96, present on SciMLBase master), pulled into these docs via modules = [..., Optimization.SciMLBase, ...]. The page optimization_packages/optimization does not exist (the Sophia example lives at optimization_packages/sophia/), so docs.sciml.ai returns 403 for the missing path (it returns 200 for real pages, so this is a genuine broken link, not bot-blocking). Fix belongs in SciML/SciMLBase.jl (repoint to optimization_packages/sophia/); a SciMLBase release must then propagate before this repo's docs build can go fully green.

So this PR makes all of Optimization.jl's own docs problems pass; the last red is a SciMLBase upstream docstring link. Please ignore until reviewed by @ChrisRackauckas.