add search to skills view

i think there's a lot more we can/should/will do with the skills view, but one tiny thing that's missing: a search bar!

i was just trying to find the `/review` skill (turns out it's built-in to claude code, not a skill i have somewhere, but anyways......) and scrolling was a bit painful since we have a ton of built-in skills, and i have the posthog repo locally which also has a ton of skills