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/NewIssueDialog.test.tsx

@@ -222,6 +222,25 @@ async function flush() {
   });
 }
 
+async function typeTextareaValue(textarea: HTMLTextAreaElement, value: string) {
+  await act(async () => {
+    const valueSetter = Object.getOwnPropertyDescriptor(
+      window.HTMLTextAreaElement.prototype,
+      "value",
+    )?.set;
+    valueSetter?.call(textarea, value);
+    textarea.dispatchEvent(
+      new InputEvent("input", {
+        bubbles: true,
+        data: value,
+        inputType: "insertText",
+      }),
+    );
+    textarea.dispatchEvent(new Event("change", { bubbles: true }));
+  });
+  await flush();
+}
+
 async function waitForAssertion(assertion: () => void, attempts = 20) {
   let lastError: unknown;
 
@@ -260,6 +279,7 @@ describe("NewIssueDialog", () => {
   let container: HTMLDivElement;
 
   beforeEach(() => {
+    vi.useRealTimers();
     container = document.createElement("div");
     document.body.appendChild(container);
     dialogState.newIssueOpen = true;
@@ -411,25 +431,8 @@ describe("NewIssueDialog", () => {
     expect(titleInput).not.toBeNull();
     expect(descriptionInput).not.toBeNull();
 
-    await act(async () => {
-      const valueSetter = Object.getOwnPropertyDescriptor(
-        HTMLTextAreaElement.prototype,
-        "value",
-      )?.set;
-      valueSetter?.call(titleInput, "Typed issue");
-      titleInput!.dispatchEvent(new Event("input", { bubbles: true }));
-    });
-    await flush();
-
-    await act(async () => {
-      const valueSetter = Object.getOwnPropertyDescriptor(
-        HTMLTextAreaElement.prototype,
-        "value",
-      )?.set;
-      valueSetter?.call(descriptionInput, "Typed description");
-      descriptionInput!.dispatchEvent(new Event("input", { bubbles: true }));
-    });
-    await flush();
+    await typeTextareaValue(titleInput!, "Typed issue");
+    await typeTextareaValue(descriptionInput!, "Typed description");
 
     await act(async () => {
       resolveProjects([
@@ -448,7 +451,7 @@ describe("NewIssueDialog", () => {
     const submitButton = Array.from(container.querySelectorAll("button"))
       .find((button) => button.textContent?.includes("Create Issue"));
     expect(submitButton).not.toBeUndefined();
-    await waitForAssertion(() => {
+    await vi.waitFor(() => {
       expect(submitButton?.hasAttribute("disabled")).toBe(false);
     });