more useful build logs to indicate progress

Describe the problem

Currently, the Svelte Kit build logs lack information about what is being built/processed, making it difficult to track build progress and identify potentially slow parts.

This becomes increasingly problematic with larger projects where numerous routes and components exist. Build logs are just multiple thousand lines of the generated chunks, which for my case and potentially other bigger projects is kinda redundant.

An example build can be found here.

Describe the proposed solution

I would love to see following informations during build:

• what route has been compiled
• only show chunks are over the size limit - not all
• when server and client side bundling starts/ends
• etc

Even better if these are configurable with log levels to adjust verbosity. I know that some of the logs come from vite itself, so it might get a bit tricky here configuration-wise.

Alternatives considered

For debugging build progress, I have been using the profiler and debug flag for vite build. However there is a lot of noise.

Importance

nice to have

Additional Information

Only related issue I found was #8309

Start with the Vite build invoked by SvelteKit, comparing normal output with the profiler and debug flag mentioned in the issue. Define how route progress, server/client bundling phases, and oversized chunks should be reported, then determine how configurable log verbosity could cover these messages without the existing chunk noise.