[codex] Split PR #4692 UI/QoL updates (#4701)

## Thinking Path

> - Paperclip orchestrates AI agents through a company-scoped control
plane.
> - The affected surface is the board UI for issue threads, issue lists,
routines, dialogs, navigation, and issue review indicators.
> - Closed PR #4692 bundled backend, schema, docs, workflow, and UI/QoL
work into one oversized change set.
> - Greptile could not keep reviewing that broad PR because it exceeded
the 100-file review limit and mixed unrelated concerns.
> - This pull request extracts the UI/QoL slice into a fresh branch
under the review limit while leaving workflow and lockfile churn out.
> - The benefit is a focused review path for the board UI performance
and workflow improvements without reopening the oversized PR.

## What Changed

- Added long issue-thread virtualization, scroll-container binding,
anchor preservation, latest-comment jump targeting, and related
regression/perf fixtures.
- Improved issue list scalability with scroll-based loading, server
offset parameters, and pagination-focused UI tests.
- Reduced new issue dialog typing churn and split dialog action
subscriptions so broad layout/nav surfaces avoid unnecessary renders.
- Added routine variables help and routine description mention options
for users, agents, and projects.
- Added productivity review badge/link UI and fixed the badge to use
Paperclip's company-prefixed router link.
- Kept the split PR below Greptile's review limit and excluded
`.github/workflows/pr.yml` and `pnpm-lock.yaml`.

## Verification

- `pnpm install --no-frozen-lockfile` in the clean worktree to install
`@tanstack/react-virtual` locally without committing lockfile churn.
- `pnpm --filter @paperclipai/ui exec vitest run --config
vitest.config.ts src/components/IssueChatThread.test.tsx
src/components/IssuesList.test.tsx
src/components/NewIssueDialog.test.tsx src/pages/Routines.test.tsx
src/pages/Issues.test.tsx` passed: 5 files, 83 tests.
- `pnpm --filter @paperclipai/ui typecheck` passed.
- `git diff --check origin/master..HEAD` passed.
- Split-scope checks: 53 changed files; no `.github/workflows/pr.yml`;
no `pnpm-lock.yaml`.
- Screenshots were not captured in this heartbeat; the changes are
primarily virtualization, routing, pagination, and editor behavior
covered by focused regression tests.

## Risks

- Moderate UI risk because issue-thread virtualization changes scroll
behavior on long conversations; regression tests cover anchor jumps,
latest-comment targeting, row metadata, and short-thread fallback.
- Moderate integration risk because the issue-list offset parameter and
productivity review field depend on matching API behavior.
- Dependency risk: the UI package adds `@tanstack/react-virtual` while
repository policy keeps `pnpm-lock.yaml` out of PRs, so CI must resolve
dependency changes through the repo's normal lockfile policy.

> For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and
discuss it in `#dev` before opening the PR. Feature PRs that overlap
with planned core work may need to be redirected — check the roadmap
first. See `CONTRIBUTING.md`.

## Model Used

- OpenAI Codex, GPT-5 coding agent, tool-enabled local repository and
GitHub workflow. Exact runtime context window was not exposed by the
harness.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [ ] If this change affects the UI, I have included before/after
screenshots
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

---------

Co-authored-by: Paperclip <noreply@paperclip.ing>

ui/src/App.tsx

@@ -14,6 +14,7 @@ import { ProjectWorkspaceDetail } from "./pages/ProjectWorkspaceDetail";
 import { Workspaces } from "./pages/Workspaces";
 import { Issues } from "./pages/Issues";
 import { IssueDetail } from "./pages/IssueDetail";
+import { IssueChatLongThreadPerf } from "./pages/IssueChatLongThreadPerf";
 import { Routines } from "./pages/Routines";
 import { RoutineDetail } from "./pages/RoutineDetail";
 import { UserProfile } from "./pages/UserProfile";
@@ -50,7 +51,7 @@ import { InviteLandingPage } from "./pages/InviteLanding";
 import { JoinRequestQueue } from "./pages/JoinRequestQueue";
 import { NotFoundPage } from "./pages/NotFound";
 import { useCompany } from "./context/CompanyContext";
-import { useDialog } from "./context/DialogContext";
+import { useDialogActions } from "./context/DialogContext";
 import { loadLastInboxTab } from "./lib/inbox";
 import { shouldRedirectCompanylessRouteToOnboarding } from "./lib/onboarding-route";
 
@@ -98,6 +99,9 @@ function boardRoutes() {
       <Route path="issues/done" element={<Navigate to="/issues" replace />} />
       <Route path="issues/recent" element={<Navigate to="/issues" replace />} />
       <Route path="issues/:issueId" element={<IssueDetail />} />
+      {import.meta.env.DEV ? (
+        <Route path="tests/perf/long-thread" element={<IssueChatLongThreadPerf />} />
+      ) : null}
       <Route path="routines" element={<Routines />} />
       <Route path="routines/:routineId" element={<RoutineDetail />} />
       <Route path="execution-workspaces/:workspaceId" element={<ExecutionWorkspaceDetail />} />
@@ -139,7 +143,7 @@ function LegacySettingsRedirect() {
 
 function OnboardingRoutePage() {
   const { companies } = useCompany();
-  const { openOnboarding } = useDialog();
+  const { openOnboarding } = useDialogActions();
   const { companyPrefix } = useParams<{ companyPrefix?: string }>();
   const matchedCompany = companyPrefix
     ? companies.find((company) => company.issuePrefix.toUpperCase() === companyPrefix.toUpperCase()) ?? null
@@ -231,7 +235,7 @@ function UnprefixedBoardRedirect() {
 }
 
 function NoCompaniesStartPage() {
-  const { openOnboarding } = useDialog();
+  const { openOnboarding } = useDialogActions();
 
   return (
     <div className="mx-auto max-w-xl py-10">