[codex] Improve issue thread review flow (#4381)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies
> - Issue detail is where operators coordinate review, approvals, and
follow-up work with active runs
> - That thread UI needs to surface blockers, descendants, review
handoffs, and reply ergonomics clearly enough for humans to guide agent
work
> - Several small gaps in the issue-thread flow were making review and
navigation clunkier than necessary
> - This pull request improves the reply composer, descendant/blocker
presentation, interaction folding, and review-request handoff plumbing
together as one cohesive issue-thread workflow slice
> - The benefit is a cleaner operator review loop without changing the
broader task model

## What Changed

- restored and refined the floating reply composer behavior in the issue
thread
- folded expired confirmation interactions and improved post-submit
thread scrolling behavior
- surfaced descendant issue context and inline blocker/paused-assignee
notices on the issue detail view
- tightened large-board first paint behavior in `IssuesList`
- added loose review-request handoffs through the issue
execution-policy/update path and covered them with tests

## Verification

- `pnpm vitest run ui/src/pages/IssueDetail.test.tsx`
- `pnpm vitest run server/src/__tests__/issues-service.test.ts
server/src/__tests__/issue-execution-policy.test.ts`
- `pnpm exec vitest run --project @paperclipai/ui
ui/src/components/IssueChatThread.test.tsx
ui/src/components/IssueProperties.test.tsx
ui/src/components/IssuesList.test.tsx ui/src/lib/issue-tree.test.ts
ui/src/api/issues.test.ts`
- `pnpm exec vitest run --project @paperclipai/adapter-utils
packages/adapter-utils/src/server-utils.test.ts`
- `pnpm exec vitest run --project @paperclipai/server
server/src/__tests__/issue-comment-reopen-routes.test.ts -t "coerces
executor handoff patches into workflow-controlled review wakes|wakes the
return assignee with execution_changes_requested"`
- `pnpm exec vitest run --project @paperclipai/server
server/src/__tests__/issue-execution-policy.test.ts
server/src/__tests__/issues-service.test.ts`

## Visual Evidence

- UI layout changes are covered by the focused issue-thread component
and issue-detail tests listed above. Browser screenshots were not
attachable from this automated greploop environment, so reviewers should
use the running preview for final visual confirmation.

## Risks

- Moderate UI-flow risk: these changes touch the issue detail experience
in multiple spots, so regressions would most likely show up as
thread-layout quirks or incorrect review-handoff behavior

> 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-based coding agent with tool use and code execution
in the Codex CLI environment

## 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
- [x] If this change affects the UI, I have included before/after
screenshots or documented the visual verification path
- [ ] 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/components/IssuesList.test.tsx

@@ -22,6 +22,8 @@ const mockIssuesApi = vi.hoisted(() => ({
   listLabels: vi.fn(),
 }));
 
+const mockKanbanBoard = vi.hoisted(() => vi.fn());
+
 const mockAuthApi = vi.hoisted(() => ({
   getSession: vi.fn(),
 }));
@@ -87,7 +89,16 @@ vi.mock("./IssueRow", () => ({
 }));
 
 vi.mock("./KanbanBoard", () => ({
-  KanbanBoard: () => null,
+  KanbanBoard: (props: { issues: Issue[] }) => {
+    mockKanbanBoard(props);
+    return (
+      <div data-testid="kanban-board">
+        {props.issues.map((issue) => (
+          <span key={issue.id}>{issue.title}</span>
+        ))}
+      </div>
+    );
+  },
 }));
 
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
@@ -189,6 +200,7 @@ describe("IssuesList", () => {
     container = document.createElement("div");
     document.body.appendChild(container);
     dialogState.openNewIssue.mockReset();
+    mockKanbanBoard.mockReset();
     mockIssuesApi.list.mockReset();
     mockIssuesApi.listLabels.mockReset();
     mockAuthApi.getSession.mockReset();
@@ -404,6 +416,113 @@ describe("IssuesList", () => {
     });
   });
 
+  it("loads board issues with a separate result limit for each status column", async () => {
+    localStorage.setItem(
+      "paperclip:test-issues:company-1",
+      JSON.stringify({ viewMode: "board" }),
+    );
+
+    const parentIssue = createIssue({
+      id: "issue-parent-total-limit",
+      title: "Parent total-limited issue",
+      status: "todo",
+    });
+    const backlogIssue = createIssue({
+      id: "issue-backlog",
+      title: "Backlog column issue",
+      status: "backlog",
+    });
+    const doneIssue = createIssue({
+      id: "issue-done",
+      title: "Done column issue",
+      status: "done",
+    });
+
+    mockIssuesApi.list.mockImplementation((_companyId, filters) => {
+      if (filters?.status === "backlog") return Promise.resolve([backlogIssue]);
+      if (filters?.status === "done") return Promise.resolve([doneIssue]);
+      return Promise.resolve([]);
+    });
+
+    const { root } = renderWithQueryClient(
+      <IssuesList
+        issues={[parentIssue]}
+        agents={[]}
+        projects={[]}
+        viewStateKey="paperclip:test-issues"
+        enableRoutineVisibilityFilter
+        onUpdateIssue={() => undefined}
+      />,
+      container,
+    );
+
+    await waitForAssertion(() => {
+      expect(mockIssuesApi.list).toHaveBeenCalledWith("company-1", expect.objectContaining({
+        status: "backlog",
+        limit: 200,
+        includeRoutineExecutions: true,
+      }));
+      expect(mockIssuesApi.list).toHaveBeenCalledWith("company-1", expect.objectContaining({
+        status: "done",
+        limit: 200,
+        includeRoutineExecutions: true,
+      }));
+      expect(mockKanbanBoard).toHaveBeenLastCalledWith(expect.objectContaining({
+        issues: expect.arrayContaining([
+          expect.objectContaining({ id: "issue-backlog" }),
+          expect.objectContaining({ id: "issue-done" }),
+        ]),
+      }));
+      expect(container.textContent).toContain("Backlog column issue");
+      expect(container.textContent).toContain("Done column issue");
+      expect(container.textContent).not.toContain("Parent total-limited issue");
+    });
+
+    act(() => {
+      root.unmount();
+    });
+  });
+
+  it("shows a refinement hint when a board column hits its server cap", async () => {
+    localStorage.setItem(
+      "paperclip:test-issues:company-1",
+      JSON.stringify({ viewMode: "board" }),
+    );
+
+    const cappedBacklogIssues = Array.from({ length: 200 }, (_, index) =>
+      createIssue({
+        id: `issue-backlog-${index + 1}`,
+        identifier: `PAP-${index + 1}`,
+        title: `Backlog issue ${index + 1}`,
+        status: "backlog",
+      }),
+    );
+
+    mockIssuesApi.list.mockImplementation((_companyId, filters) => {
+      if (filters?.status === "backlog") return Promise.resolve(cappedBacklogIssues);
+      return Promise.resolve([]);
+    });
+
+    const { root } = renderWithQueryClient(
+      <IssuesList
+        issues={[]}
+        agents={[]}
+        projects={[]}
+        viewStateKey="paperclip:test-issues"
+        onUpdateIssue={() => undefined}
+      />,
+      container,
+    );
+
+    await waitForAssertion(() => {
+      expect(container.textContent).toContain("Some board columns are showing up to 200 issues. Refine filters or search to reveal the rest.");
+    });
+
+    act(() => {
+      root.unmount();
+    });
+  });
+
   it("caps the first paint for large issue lists", async () => {
     const manyIssues = Array.from({ length: 220 }, (_, index) =>
       createIssue({