[codex] Add issue subtree pause, cancel, and restore controls (#4332)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies.
> - This branch extends the issue control-plane so board operators can
pause, cancel, and later restore whole issue subtrees while keeping
descendant execution and wake behavior coherent.
> - That required new hold state in the database, shared contracts,
server routes/services, and issue detail UI controls so subtree actions
are durable and auditable instead of ad hoc.
> - While this branch was in flight, `master` advanced with new
environment lifecycle work, including a new `0065_environments`
migration.
> - Before opening the PR, this branch had to be rebased onto
`paperclipai/paperclip:master` without losing the existing
subtree-control work or leaving conflicting migration numbering behind.
> - This pull request rebases the subtree pause/cancel/restore feature
cleanly onto current `master`, renumbers the hold migration to
`0066_issue_tree_holds`, and preserves the full branch diff in a single
PR.
> - The benefit is that reviewers get one clean, mergeable PR for the
subtree-control feature instead of stale branch history with migration
conflicts.

## What Changed

- Added durable issue subtree hold data structures, shared
API/types/validators, server routes/services, and UI flows for subtree
pause, cancel, and restore operations.
- Added server and UI coverage for subtree previewing, hold
creation/release, dependency-aware scheduling under holds, and issue
detail subtree controls.
- Rebased the branch onto current `paperclipai/paperclip:master` and
renumbered the branch migration from `0065_issue_tree_holds` to
`0066_issue_tree_holds` so it no longer conflicts with upstream
`0065_environments`.
- Added a small follow-up commit that makes restore requests return `200
OK` explicitly while keeping pause/cancel hold creation at `201
Created`, and updated the route test to match that contract.

## Verification

- `pnpm --filter @paperclipai/db typecheck`
- `pnpm --filter @paperclipai/shared typecheck`
- `pnpm --filter @paperclipai/server typecheck`
- `pnpm --filter @paperclipai/ui typecheck`
- `cd server && pnpm exec vitest run
src/__tests__/issue-tree-control-routes.test.ts
src/__tests__/issue-tree-control-service.test.ts
src/__tests__/issue-tree-control-service-unit.test.ts
src/__tests__/heartbeat-dependency-scheduling.test.ts`
- `cd ui && pnpm exec vitest run src/components/IssueChatThread.test.tsx
src/pages/IssueDetail.test.tsx`

## Risks

- This is a broad cross-layer change touching DB/schema, shared
contracts, server orchestration, and UI; regressions are most likely
around subtree status restoration or wake suppression/resume edge cases.
- The migration was renumbered during PR prep to avoid the new upstream
`0065_environments` conflict. Reviewers should confirm the final
`0066_issue_tree_holds` ordering is the only hold-related migration that
lands.
- The issue-tree restore endpoint now responds with `200` instead of
relying on implicit behavior, which is semantically better for a restore
operation but still changes an API detail that clients or tests could
have assumed.

> 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 coding agent in the Paperclip Codex runtime (GPT-5-class
tool-using coding model; exact deployment ID/context window is not
exposed inside this session).

## 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
- [ ] 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/api/issues.ts

@@ -1,6 +1,7 @@
 import type {
   AskUserQuestionsAnswer,
   Approval,
+  CreateIssueTreeHold,
   DocumentRevision,
   FeedbackTargetType,
   FeedbackTrace,
@@ -11,7 +12,11 @@ import type {
   IssueDocument,
   IssueLabel,
   IssueThreadInteraction,
+  IssueTreeControlPreview,
+  IssueTreeHold,
   IssueWorkProduct,
+  PreviewIssueTreeControl,
+  ReleaseIssueTreeHold,
   UpsertIssueDocument,
 } from "@paperclipai/shared";
 import { api } from "./client";
@@ -79,6 +84,41 @@ export const issuesApi = {
     api.post<Issue>(`/companies/${companyId}/issues`, data),
   update: (id: string, data: Record<string, unknown>) =>
     api.patch<IssueUpdateResponse>(`/issues/${id}`, data),
+  previewTreeControl: (id: string, data: PreviewIssueTreeControl) =>
+    api.post<IssueTreeControlPreview>(`/issues/${id}/tree-control/preview`, data),
+  createTreeHold: (id: string, data: CreateIssueTreeHold) =>
+    api.post<{ hold: IssueTreeHold; preview: IssueTreeControlPreview }>(`/issues/${id}/tree-holds`, data),
+  getTreeHold: (id: string, holdId: string) =>
+    api.get<IssueTreeHold>(`/issues/${id}/tree-holds/${holdId}`),
+  listTreeHolds: (
+    id: string,
+    filters?: {
+      status?: "active" | "released";
+      mode?: "pause" | "resume" | "cancel" | "restore";
+      includeMembers?: boolean;
+    },
+  ) => {
+    const params = new URLSearchParams();
+    if (filters?.status) params.set("status", filters.status);
+    if (filters?.mode) params.set("mode", filters.mode);
+    if (filters?.includeMembers) params.set("includeMembers", "true");
+    const qs = params.toString();
+    return api.get<IssueTreeHold[]>(`/issues/${id}/tree-holds${qs ? `?${qs}` : ""}`);
+  },
+  getTreeControlState: (id: string) =>
+    api.get<{
+      activePauseHold: {
+        holdId: string;
+        rootIssueId: string;
+        issueId: string;
+        isRoot: boolean;
+        mode: "pause";
+        reason: string | null;
+        releasePolicy: { strategy: "manual" | "after_active_runs_finish"; note?: string | null } | null;
+      } | null;
+    }>(`/issues/${id}/tree-control/state`),
+  releaseTreeHold: (id: string, holdId: string, data: ReleaseIssueTreeHold) =>
+    api.post<IssueTreeHold>(`/issues/${id}/tree-holds/${holdId}/release`, data),
   remove: (id: string) => api.delete<Issue>(`/issues/${id}`),
   checkout: (id: string, agentId: string) =>
     api.post<Issue>(`/issues/${id}/checkout`, {