Fix stable problem-trait documentation links

[ChrisRackauckas-Claude]

Ignore this PR until it has been reviewed by @ChrisRackauckas.

Summary

• redirect the 16 portable problem_type docstring links from the undeployed stable Problem_Traits page
• use the long-standing stable Problems/#Problem-Traits section instead
• keep strict Documenter link checking enabled

Root cause

PR #1468 introduced absolute links to https://docs.sciml.ai/SciMLBase/stable/interfaces/Problem_Traits/. The page exists in current source and in the GitHub Pages dev tree, but the deployed stable documentation is still v3.22 and does not contain that route. The CloudFront/S3 endpoint therefore returns HTTP 403, causing every documentation build since #1468 to fail strict link checking.

The replacement target exists in both v3.22 and current sources and returns HTTP 200. It retains a portable absolute link for docstrings rendered by downstream documentation sites.

Investigation trail

1. Reproduced the 403 with curl and an untouched checkout of upstream master b6e131a37.
2. Ran the full local docs build and observed makedocs terminate with [:linkcheck] on the same URL.
3. Compared hosted documentation history: the immediately preceding master run 30035957346 passed; PR Portable absolute URLs for docstring @refs that break DiffEqDocs (#879) #1468 run 30072174284 was the first to fail with the exact URL.
4. Verified commit 6807f7fd5 introduced all affected links.
5. Replaced only those links and reran the same strict build successfully.

Validation

• timeout 3600 julia +1.12 --color=yes --project=docs docs/make.jl — passed, including strict linkcheck and HTML rendering
• timeout 3600 env GROUP=Core julia +1.12 --color=yes --project=. -e 'using Pkg; Pkg.test()' — passed (SciMLBase tests passed)
• Runic 1.7.0 whole-repository --check — passed
• git diff --check — passed
• curl of the replacement URL — HTTP 200

The existing strict documentation build is the regression test for the broken external link. No link is ignored or downgraded to a warning.