Summary

Bug from #3166: scrolling inside an agent / provider / skill drawer past its top or bottom edge propagated the wheel gesture to the underlying page. The drawer variant intentionally leaves the page interactive (no dim backdrop, pointer-events-none on the container), so scroll chaining was visible — the page slid under the drawer mid-scroll, jarring.

Fix

One Tailwind class on Modal's scroll wrapper:

- <div className="flex-1 overflow-y-auto scrollbar-thin">{children}</div>
+ <div className="flex-1 overflow-y-auto overscroll-contain scrollbar-thin">{children}</div>

overscroll-behavior: contain tells the browser to stop the wheel event at this element's boundary instead of propagating to ancestors. Standard CSS, well-supported.

The change applies to centred modals too, which silently fixes a pre-existing papercut: a long modal over a long page used to scroll the page once the modal bottomed out, even though the dim backdrop suggested the page was locked.

Test plan

• Manual: open agent drawer with long detail content, scroll inside drawer past bottom → underlying agents list should NOT scroll (it did before this PR)
• Manual: same for provider / skill / hand drawers (feat(dashboard): convert hand detail panel to drawer variant #3168 still in flight covers HandsPage)
• Manual centred-modal regression: open Tools editor or Create Agent modal over a scrolled-down list, scroll past modal bottom → list should NOT scroll
• CI green