### Summary
Adopt sync.WaitGroup.Go (Go 1.25) to simplify tracked goroutine
spawning. This replaces the error-prone trio of wg.Add(1), go func(),
and defer wg.Done() with a single, self-contained call.
More info: https://github.com/golang/go/issues/63796
Signed-off-by: grandpig <grandpig@outlook.com>
Replace fragile wall-clock timeout assertions with semantic checks for
deadline errors, retry suppression, and event ordering. Keep only
lower-bound timing checks where they prove backoff behavior. This
reduces CPU-load flakes without weakening regression coverage.
## Summary
Two changes to make Go build \& run independent of native libraries
(office_oxide, pdfium, pdf_oxide).
## 1. Make native libraries optional (build.sh + Go source)
## 2. Roll back tests.yml CI changes from PR #16391
### What problem does this PR solve?
Package refactor and PDF post process.
### Type of change
- [x] Refactoring
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Co-authored-by: Claude <noreply@anthropic.com>
