dillon1000/react

[DevTools] Show "Initial Paint" in the breadcrumbs when root is selected (#34652)

We selected the root. This means that we're currently viewing the
Transition that rendered the whole screen. In laymans terms this is
really "Initial Paint". Once we add subtree selection, then the
equivalent should be called "Transition" since in that case it's really
about a Transition within the page. So if you've selected an Activity
tree this should be called "Transition".

Once we add the environment support to the timeline. The first entry on
the timeline should also be called "Initial Paint" when you haven't
selected an Activity and "Transition" when you have.

Technically they're both meant to be "Transition" but nobody thinks of
initial load as a "Transition" from the previous MPA page.

<img width="1214" height="419" alt="Screenshot 2025-09-29 at 5 18 58 PM"
src="https://github.com/user-attachments/assets/cae263e3-133c-4fa9-9587-a7b2344199f4"
/>