[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__/issue-execution-policy.test.ts

@@ -171,6 +171,75 @@ describe("issue execution policy transitions", () => {
       expect(result.decision).toBeUndefined();
     });
 
+    it("carries loose review instructions on the pending handoff", () => {
+      const reviewInstructions = [
+        "Please focus on whether the migration path is reversible.",
+        "",
+        "- Check failure handling",
+        "- Call out any unclear operator instructions",
+      ].join("\n");
+
+      const result = applyIssueExecutionPolicyTransition({
+        issue: {
+          status: "in_progress",
+          assigneeAgentId: coderAgentId,
+          assigneeUserId: null,
+          executionPolicy: policy,
+          executionState: null,
+        },
+        policy,
+        requestedStatus: "done",
+        requestedAssigneePatch: {},
+        actor: { agentId: coderAgentId },
+        commentBody: "Implemented the migration",
+        reviewRequest: { instructions: reviewInstructions },
+      });
+
+      expect(result.patch.executionState).toMatchObject({
+        status: "pending",
+        currentStageType: "review",
+        currentParticipant: { type: "agent", agentId: qaAgentId },
+        reviewRequest: { instructions: reviewInstructions },
+      });
+    });
+
+    it("clears loose review instructions with explicit null during a stage transition", () => {
+      const reviewStageId = policy.stages[0].id;
+      const result = applyIssueExecutionPolicyTransition({
+        issue: {
+          status: "in_progress",
+          assigneeAgentId: coderAgentId,
+          assigneeUserId: null,
+          executionPolicy: policy,
+          executionState: {
+            status: "pending",
+            currentStageId: reviewStageId,
+            currentStageIndex: 0,
+            currentStageType: "review",
+            currentParticipant: { type: "agent", agentId: qaAgentId },
+            returnAssignee: { type: "agent", agentId: coderAgentId },
+            reviewRequest: { instructions: "Old review request" },
+            completedStageIds: [],
+            lastDecisionId: null,
+            lastDecisionOutcome: null,
+          },
+        },
+        policy,
+        requestedStatus: "in_review",
+        requestedAssigneePatch: {},
+        actor: { agentId: coderAgentId },
+        commentBody: "Ready for review",
+        reviewRequest: null,
+      });
+
+      expect(result.patch.executionState).toMatchObject({
+        status: "pending",
+        currentStageType: "review",
+        currentParticipant: { type: "agent", agentId: qaAgentId },
+        reviewRequest: null,
+      });
+    });
+
     it("reviewer approves → advances to approval stage", () => {
       const reviewStageId = policy.stages[0].id;
       const result = applyIssueExecutionPolicyTransition({
@@ -214,6 +283,44 @@ describe("issue execution policy transitions", () => {
       });
     });
 
+    it("lets a reviewer provide loose instructions for the next approval stage", () => {
+      const reviewStageId = policy.stages[0].id;
+      const approvalInstructions = "Please decide whether this is ready to ship, with any launch caveats.";
+      const result = applyIssueExecutionPolicyTransition({
+        issue: {
+          status: "in_review",
+          assigneeAgentId: qaAgentId,
+          assigneeUserId: null,
+          executionPolicy: policy,
+          executionState: {
+            status: "pending",
+            currentStageId: reviewStageId,
+            currentStageIndex: 0,
+            currentStageType: "review",
+            currentParticipant: { type: "agent", agentId: qaAgentId },
+            returnAssignee: { type: "agent", agentId: coderAgentId },
+            reviewRequest: { instructions: "Review the implementation details." },
+            completedStageIds: [],
+            lastDecisionId: null,
+            lastDecisionOutcome: null,
+          },
+        },
+        policy,
+        requestedStatus: "done",
+        requestedAssigneePatch: {},
+        actor: { agentId: qaAgentId },
+        commentBody: "QA signoff complete",
+        reviewRequest: { instructions: approvalInstructions },
+      });
+
+      expect(result.patch.executionState).toMatchObject({
+        status: "pending",
+        currentStageType: "approval",
+        currentParticipant: { type: "user", userId: ctoUserId },
+        reviewRequest: { instructions: approvalInstructions },
+      });
+    });
+
     it("approver approves → marks completed (allows done)", () => {
       const reviewStageId = policy.stages[0].id;
       const approvalStageId = policy.stages[1].id;