Summary

Replaces server-side cookie reading (getResizableSnapshot) with client-side localStorage for persisting resizable panel sizes on two routes. Cookies were hitting the ~4KB size limit; localStorage supports 5–10MB.

Two routes modified, two approaches used:

1. Run detail route (runs.$runParam/route.tsx): Adds a Remix clientLoader with hydrate = true that reads panel snapshots from localStorage before first render via a getLocalStorageSnapshot helper that validates the stored JSON shape.

2. Prompts route (prompts.$promptSlug/route.tsx): Simply removes the server-side cookie reads and returns undefined for snapshots. The react-window-splitter library already defaults to autosaveStrategy="localStorage" and reads from it when no snapshot prop is provided. A clientLoader was not used here because this route uses remix-typedjson (typedjson/useTypedLoaderData), which doesn't compose cleanly with clientLoader.

In both cases the library continues to automatically write to localStorage on resize (via autosaveId), so no save-side changes were needed. The resizablePanel.server module is left intact as it may be used by other routes.

Review & Testing Checklist for Human

• Prompts route panel restore: Resize the outer/vertical/generations panels on the prompts page, reload, and verify sizes are restored. Since there's no clientLoader here, the library's built-in localStorage read is doing the work — confirm it actually kicks in when snapshot is undefined (keys: prompt-detail, prompt-vertical, prompt-generations)
• Run detail route panel restore: Resize parent/tree panels, reload, verify sizes restore from localStorage (keys: panel-run-parent-v2, panel-run-tree)
• No hydration errors in browser console on initial load of both routes — the clientLoader.hydrate = true pattern on the run detail route is the highest-risk area for hydration mismatches

Notes

• Old cookie data from the previous approach remains in users' browsers but is harmless — it simply won't be read anymore.
• The getLocalStorageSnapshot helper checks for a "status" property to validate the stored shape. If the library ever changes its serialization format, this silently falls back to default panel sizes rather than crashing.
• The two different approaches (explicit clientLoader vs. library-native) are intentional due to the remix-typedjson constraint but could be unified later if remix-typedjson is removed from the prompts route.

Link to Devin session: https://app.devin.ai/sessions/2e69f1933945442e9daba486837a6f5b
Requested by: @ericallam