[clang-tidy] Check bugprone-unchecked-optional-access triggers a false-positive related to nested loops

This code triggers a false-positive result from clang-tidy check bugprone-unchecked-optional-access (see https://godbolt.org/z/joe53TMs4):

```c++
#include
#include

struct Dependency
{
std::optional m_valuePart;
};

void process(const std::list& dependencies, const std::list& values)
{
for (const Dependency& dependency : dependencies) // outer loop
{
for (int val : values) // inner loop — unrelated to dependency
{
if (dependency.m_valuePart.has_value()) // std::optional check
{
int vp = dependency.m_valuePart.value(); // <-- false positive
}
}
}
}
```

The issue occurs on the main branch (upcoming clang 23) but is present at least since clang 21.

Start by reproducing the provided nested-loop example on the main branch and inspect the implementation and tests for bugprone-unchecked-optional-access. Trace why the inner loop invalidates the has_value() reasoning, then add a regression test and confirm the false-positive diagnostic is gone without weakening valid warnings.

Written by the indexing model from the issue text.