fix(inbox): refetch + virtualize + server-search the people pickers

[Twixes]

Problem

The inbox assignee / "Entire project" scope selector broke: it didn't re-fetch, so the people list went stale (reported by Olly/Rafa in Slack). While in there, the PostHog/code people listings in both Reviewers and Entire project also needed: a virtualized list, server-side search, and a helpful empty state.

Changes

• New shared PeoplePickerList — a searchable, virtualized people list (only visible rows mount, so it stays responsive for large orgs) with the empty-state hint.
• New shared useReviewerPickerOptions hook driving server-side search through the available_reviewers ?query= param (debounced), and pinning "me" only on the unfiltered base list.
• Reviewers picker (SuggestedReviewersSection) and inbox scope picker (InboxScopeSelect) both rewired onto the shared list.
• Re-fetch bug fix: the scope dropdown's data now lives inside a Popover whose content only mounts while open, so the query re-mounts and re-fetches on every open instead of staying mounted and stale.
• Empty state: when no people match, the dropdown shows "Someone not showing up here? Ask them to connect their GitHub profile with PostHog", linking to the personal settings page (/settings/user).

Note on "fetch missing entries as you scroll": the available_reviewers endpoint returns the full set of people in one response (a UUID→person dict, no count/pagination), so there are no missing pages to fetch — virtualization covers the rendering cost. True incremental fetch-on-scroll would need a paginated backend endpoint (in the posthog Django repo) first; the shared list is structured so it can be extended to infinite scroll if/when that lands.

How did you test this?

• pnpm build (all packages) — green.
• pnpm --filter @posthog/ui typecheck — green.
• biome check on the changed/added files — clean.
• No existing tests reference these components; mobile uses its own separate inbox flow and is unaffected.

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

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Created with PostHog Code from a Slack thread

[github-actions]

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_{Reviewed by React Doctor for commit 9028a64.}

[greptile-apps]

Comments Outside Diff (1)

1. packages/ui/src/features/inbox/hooks/useReviewerPickerOptions.ts, line 837-841 (link)

   Unused hasResults field in returned object

   hasResults is exported in the ReviewerPickerOptions interface and computed in the hook body (!!data?.results?.length), but it is not consumed by either of the hook's two callers — ScopePickerContent and SuggestedReviewersBody — after the AddReviewerPopover refactor removed the last reference to it. The field is superfluous and should be removed along with the hasResults line in ReviewerPickerOptions.

   Prompt To Fix With AI

   This is a comment left during a code review.
   Path: packages/ui/src/features/inbox/hooks/useReviewerPickerOptions.ts
   Line: 837-841
   
   Comment:
   **Unused `hasResults` field in returned object**
   
   `hasResults` is exported in the `ReviewerPickerOptions` interface and computed in the hook body (`!!data?.results?.length`), but it is not consumed by either of the hook's two callers — `ScopePickerContent` and `SuggestedReviewersBody` — after the `AddReviewerPopover` refactor removed the last reference to it. The field is superfluous and should be removed along with the `hasResults` line in `ReviewerPickerOptions`.
   
   How can I resolve this? If you propose a fix, please make it concise.

   Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

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### Issue 1 of 1
packages/ui/src/features/inbox/hooks/useReviewerPickerOptions.ts:837-841
**Unused `hasResults` field in returned object**

`hasResults` is exported in the `ReviewerPickerOptions` interface and computed in the hook body (`!!data?.results?.length`), but it is not consumed by either of the hook's two callers — `ScopePickerContent` and `SuggestedReviewersBody` — after the `AddReviewerPopover` refactor removed the last reference to it. The field is superfluous and should be removed along with the `hasResults` line in `ReviewerPickerOptions`.

_{Reviews (1): Last reviewed commit: "fix(inbox): refetch + virtualize + serve..." | Re-trigger Greptile}