Add workflow interaction cancellation and issue cost summaries (#4862)

## Thinking Path

> - Paperclip coordinates work through issue-thread interactions, run
history, and cost telemetry.
> - Operators need workflow prompts to be cancellable and costs to be
visible at the issue level.
> - The earlier rollup mixed this workflow/cost work with database
backups, reliability recovery, thread scaling, and settings polish.
> - This pull request isolates the interaction and cost surfaces into a
reviewable slice.
> - The backend now supports cancelling pending question interactions
and summarizing issue-tree costs.
> - The UI component layer can render cancelled questions and interleave
activity with run ledger rows.

## What Changed

- Added `cancelled` as an issue-thread interaction status and result
shape for question interactions.
- Added the board-only `POST
/issues/:id/interactions/:interactionId/cancel` route and service
implementation.
- Added issue-tree cost summary support in the cost service and
`/issues/:id/cost-summary` API route.
- Extended shared cost exports and UI API/query keys for issue cost
summaries.
- Updated `IssueThreadInteractionCard` and `IssueRunLedger` components
for cancelled questions, issue cost surfaces, and activity/run
interleaving.
- Added focused server and component regression coverage.

## Verification

- `pnpm install --frozen-lockfile`
- `pnpm exec vitest run server/src/__tests__/costs-service.test.ts
server/src/__tests__/issue-thread-interaction-routes.test.ts
server/src/__tests__/issue-thread-interactions-service.test.ts
ui/src/components/IssueRunLedger.test.tsx`
- Result: 4 test files passed, 45 tests passed.
- UI screenshots not included because this PR updates reusable
components and API surfaces without wiring a new page-level layout.

## Risks

- Adds a new interaction terminal status; clients that switch
exhaustively on interaction status may need to handle `cancelled`.
- Issue-tree cost summaries use recursive issue traversal and should be
watched on unusually large issue trees.
- Page-level issue detail wiring is intentionally left to the board
QoL/issue-detail branch to keep this PR narrow.

> 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-5.5, code execution and GitHub CLI tool use, medium
reasoning effort.

## 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
- [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/components/IssueRunLedger.test.tsx

@@ -3,7 +3,7 @@
 import { act } from "react";
 import type { ComponentProps, ReactNode } from "react";
 import { createRoot, type Root } from "react-dom/client";
-import type { Issue, RunLivenessState } from "@paperclipai/shared";
+import type { ActivityEvent, Issue, RunLivenessState } from "@paperclipai/shared";
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import type { RunForIssue } from "../api/activity";
 import type { ActiveRunForIssue } from "../api/heartbeats";
@@ -62,6 +62,23 @@ function createRun(overrides: Partial<RunForIssue> = {}): RunForIssue {
   };
 }
 
+function createActivity(overrides: Partial<ActivityEvent> = {}): ActivityEvent {
+  return {
+    id: "activity-1",
+    companyId: "company-1",
+    actorType: "system",
+    actorId: "system",
+    action: "issue.updated",
+    entityType: "issue",
+    entityId: "issue-1",
+    agentId: null,
+    runId: null,
+    details: null,
+    createdAt: new Date("2026-04-18T19:57:00.000Z"),
+    ...overrides,
+  };
+}
+
 function createIssue(overrides: Partial<Issue> = {}): Issue {
   return {
     id: "issue-1",
@@ -139,6 +156,8 @@ function renderLedger(props: Partial<ComponentProps<typeof IssueRunLedgerContent
       issueStatus={props.issueStatus ?? "in_progress"}
       childIssues={props.childIssues ?? []}
       agentMap={props.agentMap ?? new Map([["agent-1", { name: "CodexCoder" }]])}
+      activityEvents={props.activityEvents}
+      renderActivityEvent={props.renderActivityEvent}
       pendingWatchdogDecision={props.pendingWatchdogDecision}
       canRecordWatchdogDecisions={props.canRecordWatchdogDecisions}
       watchdogDecisionError={props.watchdogDecisionError}
@@ -203,6 +222,42 @@ describe("IssueRunLedger", () => {
     expect(container.textContent).toContain("Last useful action Unavailable");
   });
 
+  it("interleaves run rows and activity rows by timestamp", () => {
+    renderLedger({
+      runs: [
+        createRun({
+          runId: "run-oldest",
+          startedAt: "2026-04-18T19:55:00.000Z",
+          createdAt: "2026-04-18T19:55:00.000Z",
+        }),
+        createRun({
+          runId: "run-newest",
+          startedAt: "2026-04-18T19:59:00.000Z",
+          createdAt: "2026-04-18T19:59:00.000Z",
+        }),
+      ],
+      activityEvents: [
+        createActivity({
+          id: "activity-middle",
+          action: "activity-middle",
+          createdAt: new Date("2026-04-18T19:57:00.000Z"),
+        }),
+      ],
+      renderActivityEvent: (event) => (
+        <div data-testid={`activity-${event.id}`}>{event.action}</div>
+      ),
+    });
+
+    const text = container.textContent ?? "";
+    const newestIndex = text.indexOf("run-newe");
+    const activityIndex = text.indexOf("activity-middle");
+    const oldestIndex = text.indexOf("run-olde");
+
+    expect(newestIndex).toBeGreaterThanOrEqual(0);
+    expect(activityIndex).toBeGreaterThan(newestIndex);
+    expect(oldestIndex).toBeGreaterThan(activityIndex);
+  });
+
   it("shows live runs as pending final checks without missing-data language", () => {
     renderLedger({
       runs: [
@@ -279,12 +334,18 @@ describe("IssueRunLedger", () => {
           resultJson: { stopReason: "budget_paused" },
           createdAt: "2026-04-18T19:56:00.000Z",
         }),
+        createRun({
+          runId: "run-paused",
+          resultJson: { stopReason: "paused" },
+          createdAt: "2026-04-18T19:55:00.000Z",
+        }),
       ],
     });
 
     expect(container.textContent).toContain("timeout (30s timeout)");
     expect(container.textContent).toContain("cancelled");
     expect(container.textContent).toContain("budget paused");
+    expect(container.textContent).toContain("paused by board");
   });
 
   it("surfaces active and completed child issue summaries", () => {
@@ -328,7 +389,7 @@ describe("IssueRunLedger", () => {
 
   it("shows when older runs are clipped from the ledger", () => {
     renderLedger({
-      runs: Array.from({ length: 10 }, (_, index) =>
+      runs: Array.from({ length: 22 }, (_, index) =>
         createRun({
           runId: `run-${index.toString().padStart(8, "0")}`,
           createdAt: `2026-04-18T19:${String(index).padStart(2, "0")}:00.000Z`,
@@ -336,7 +397,7 @@ describe("IssueRunLedger", () => {
       ),
     });
 
-    expect(container.textContent).toContain("2 older runs not shown");
+    expect(container.textContent).toContain("2 older items not shown");
   });
 
   it("renders stale-run banner, watchdog actions, and silence badge for live runs", () => {