[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>

server/src/__tests__/issues-service.test.ts

@@ -355,6 +355,110 @@ describeEmbeddedPostgres("issueService.list participantAgentId", () => {
     expect(result.map((issue) => issue.id)).toEqual([commentMatchId, descriptionMatchId]);
   });
 
+  it("filters issue lists to the full descendant tree for a root issue", async () => {
+    const companyId = randomUUID();
+    const rootId = randomUUID();
+    const childId = randomUUID();
+    const grandchildId = randomUUID();
+    const siblingId = randomUUID();
+
+    await db.insert(companies).values({
+      id: companyId,
+      name: "Paperclip",
+      issuePrefix: `T${companyId.replace(/-/g, "").slice(0, 6).toUpperCase()}`,
+      requireBoardApprovalForNewAgents: false,
+    });
+
+    await db.insert(issues).values([
+      {
+        id: rootId,
+        companyId,
+        title: "Root",
+        status: "todo",
+        priority: "medium",
+      },
+      {
+        id: childId,
+        companyId,
+        parentId: rootId,
+        title: "Child",
+        status: "todo",
+        priority: "medium",
+      },
+      {
+        id: grandchildId,
+        companyId,
+        parentId: childId,
+        title: "Grandchild",
+        status: "todo",
+        priority: "medium",
+      },
+      {
+        id: siblingId,
+        companyId,
+        title: "Sibling",
+        status: "todo",
+        priority: "medium",
+      },
+    ]);
+
+    const result = await svc.list(companyId, { descendantOf: rootId });
+
+    expect(new Set(result.map((issue) => issue.id))).toEqual(new Set([childId, grandchildId]));
+  });
+
+  it("combines descendant filtering with search", async () => {
+    const companyId = randomUUID();
+    const rootId = randomUUID();
+    const childId = randomUUID();
+    const grandchildId = randomUUID();
+    const outsideMatchId = randomUUID();
+
+    await db.insert(companies).values({
+      id: companyId,
+      name: "Paperclip",
+      issuePrefix: `T${companyId.replace(/-/g, "").slice(0, 6).toUpperCase()}`,
+      requireBoardApprovalForNewAgents: false,
+    });
+
+    await db.insert(issues).values([
+      {
+        id: rootId,
+        companyId,
+        title: "Root",
+        status: "todo",
+        priority: "medium",
+      },
+      {
+        id: childId,
+        companyId,
+        parentId: rootId,
+        title: "Relevant parent",
+        status: "todo",
+        priority: "medium",
+      },
+      {
+        id: grandchildId,
+        companyId,
+        parentId: childId,
+        title: "Needle grandchild",
+        status: "todo",
+        priority: "medium",
+      },
+      {
+        id: outsideMatchId,
+        companyId,
+        title: "Needle outside",
+        status: "todo",
+        priority: "medium",
+      },
+    ]);
+
+    const result = await svc.list(companyId, { descendantOf: rootId, q: "needle" });
+
+    expect(result.map((issue) => issue.id)).toEqual([grandchildId]);
+  });
+
   it("accepts issue identifiers through getById", async () => {
     const companyId = randomUUID();
     const issueId = randomUUID();