feat(issues): S4b frontend — open-issues lists + issue plumbing

- types/note.ts: Note gains systems? + arose_from_id?; TaskKind includes 'issue'.
- stores/tasks.ts: create/update accept IssueFields (kind/system_ids/arose_from_id).
- api/systems.ts: getProjectIssues + TaskLike.
- DashboardView.vue: 'Open issues' rail section from dashboard.open_issues
  (links to /tasks/<id>, project + status).
- SystemsSection.vue (project Systems tab): 'Open issues' list via getProjectIssues,
  with system chips, links to /tasks/<id>. Both reuse existing CSS tokens.

Issue-editor controls (kind selector / system multi-select / arose-from picker
in WorkspaceTaskPanel) are the remaining S4b piece. NEEDS operator browser
verification (CI typechecks only).

Refs plan 825 (S4b frontend — lists).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/api/systems.ts

@@ -42,3 +42,23 @@ export async function updateSystem(
 export async function deleteSystem(projectId: number, systemId: number): Promise<void> {
   return apiDelete(`/api/projects/${projectId}/systems/${systemId}`);
 }
+
+// Lightweight issue shape returned by the project-issues list endpoint.
+export interface TaskLike {
+  id: number;
+  title: string;
+  status: string;
+  priority: string;
+  systems?: System[];
+  updated_at?: string | null;
+}
+
+export async function getProjectIssues(
+  projectId: number,
+  openOnly = true,
+): Promise<TaskLike[]> {
+  const data = await apiGet<{ issues: TaskLike[] }>(
+    `/api/projects/${projectId}/issues?open_only=${openOnly}`,
+  );
+  return data.issues;
+}