Feature Request: Add at-a-glance indicators for experiment metrics

Feature request

Is your feature request related to a problem?

• You can only see if an experiment is working by opening them up and looking at the individual metrics.
• You can run multiple experiments at the same time.
• This means in order to see the status of each experiment, you'll have to open up each one and look them over.
• This becomes cumbersome if you have a lot of experiments going on, and you want to get a gut feeling if any of them are not succeeding.

Describe the solution you'd like

• It would be great to have a visual success indicator next to an experiment.
• Perhaps, something akin to a column showing the primary metrics in a red/yellow/green status indicator.
• Ideally, you can hover over that indicator to see the current status of the metric.
• Something like this:

Describe alternatives you've considered

• You could have the AI summarize them, or potentially create some insights.

Additional context

From https://us.posthog.com/project/2/support/tickets/74318

Debug info

- [ X] PostHog Cloud, region and project ID: [please provide, you can find both at https://app.posthog.com/settings/project-details#variables]
- [ ] PostHog Hobby self-hosted with `docker compose`, version/commit: [please provide]
- [ ] PostHog self-hosted with Kubernetes (deprecated, see [`Sunsetting Kubernetes support`](https://posthog.com/blog/sunsetting-helm-support-posthog)), version/commit: [please provide]

No files or tests are named. Start by locating the experiment overview and the existing primary-metric display, then determine where experiment status is assembled. Done should include an at-a-glance indicator for each experiment, hoverable metric status details, and coverage for the displayed states.