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>

server/src/routes/issues.ts

@@ -7,6 +7,7 @@ import { issueExecutionDecisions } from "@paperclipai/db";
 import {
   addIssueCommentSchema,
   acceptIssueThreadInteractionSchema,
+  cancelIssueThreadInteractionSchema,
   createIssueAttachmentMetadataSchema,
   createIssueThreadInteractionSchema,
   createIssueWorkProductSchema,
@@ -3182,6 +3183,58 @@ export function issueRoutes(
     },
   );
 
+  router.post(
+    "/issues/:id/interactions/:interactionId/cancel",
+    validate(cancelIssueThreadInteractionSchema),
+    async (req, res) => {
+      const id = req.params.id as string;
+      const interactionId = req.params.interactionId as string;
+      const issue = await svc.getById(id);
+      if (!issue) {
+        res.status(404).json({ error: "Issue not found" });
+        return;
+      }
+      assertCompanyAccess(req, issue.companyId);
+      assertBoard(req);
+
+      const actor = getActorInfo(req);
+      const interaction = await issueThreadInteractionService(db).cancelQuestions(issue, interactionId, req.body, {
+        agentId: actor.agentId,
+        userId: actor.actorType === "user" ? actor.actorId : null,
+      });
+
+      await logActivity(db, {
+        companyId: issue.companyId,
+        actorType: actor.actorType,
+        actorId: actor.actorId,
+        agentId: actor.agentId,
+        runId: actor.runId,
+        action: "issue.thread_interaction_cancelled",
+        entityType: "issue",
+        entityId: issue.id,
+        details: {
+          interactionId: interaction.id,
+          interactionKind: interaction.kind,
+          interactionStatus: interaction.status,
+          cancellationReason:
+            interaction.kind === "ask_user_questions"
+              ? (interaction.result?.cancellationReason ?? null)
+              : null,
+        },
+      });
+
+      queueResolvedInteractionContinuationWakeup({
+        heartbeat,
+        issue,
+        interaction,
+        actor,
+        source: "issue.interaction.cancel",
+      });
+
+      res.json(interaction);
+    },
+  );
+
   router.get("/issues/:id/comments/:commentId", async (req, res) => {
     const id = req.params.id as string;
     const commentId = req.params.commentId as string;