Fix Cloud tenant issue identifier routes (#5196)

## Summary

- Allow Cloud tenant issue identifiers with alphanumeric prefixes, such
as `PC1897-1`, to normalize as issue references.
- Resolve those identifiers through issue detail/update routes, active
run/live run polling, activity, costs, and `issueService.getById`.
- Keep UI issue-link parsing aligned so tenant links normalize back to
`/issues/<IDENTIFIER>`.

## Root Cause

Cloud tenant issue prefixes include digits from the stack-id hash. The
app-side route normalization still accepted only all-letter prefixes, so
`/api/issues/PC1897-1` skipped identifier lookup and fell through as a
non-UUID id.

## Verification

- `pnpm exec vitest run packages/shared/src/issue-references.test.ts
ui/src/lib/issue-reference.test.ts
server/src/__tests__/issue-identifier-routes.test.ts
server/src/__tests__/activity-routes.test.ts
server/src/__tests__/costs-service.test.ts
server/src/__tests__/agent-live-run-routes.test.ts
server/src/__tests__/issues-service.test.ts`
- `pnpm --filter @paperclipai/shared typecheck && pnpm --filter
@paperclipai/server typecheck`
- `git diff --check`

Co-authored-by: Paperclip <noreply@paperclip.ing>

server/src/services/issues.ts

@@ -33,7 +33,13 @@ import type {
   IssueProductivityReviewTrigger,
   IssueRelationIssueSummary,
 } from "@paperclipai/shared";
-import { clampIssueRequestDepth, extractAgentMentionIds, extractProjectMentionIds, isUuidLike } from "@paperclipai/shared";
+import {
+  clampIssueRequestDepth,
+  extractAgentMentionIds,
+  extractProjectMentionIds,
+  isUuidLike,
+  normalizeIssueIdentifier as normalizeIssueReferenceIdentifier,
+} from "@paperclipai/shared";
 import { conflict, notFound, unprocessable } from "../errors.js";
 import { parseObject } from "../adapters/utils.js";
 import {
@@ -2418,8 +2424,9 @@ export function issueService(db: Db) {
 
     getById: async (raw: string) => {
       const id = raw.trim();
-      if (/^[A-Z]+-\d+$/i.test(id)) {
-        return getIssueByIdentifier(id);
+      const identifier = normalizeIssueReferenceIdentifier(id);
+      if (identifier) {
+        return getIssueByIdentifier(identifier);
       }
       if (!isUuidLike(id)) {
         return null;