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/stores/tasks.ts

@@ -3,6 +3,16 @@ import { defineStore } from "pinia";
 import { apiGet, apiPost, apiPut, apiPatch, apiDelete } from "@/api/client";
 import { useToastStore } from "@/stores/toast";
 import type { Task, TaskStatus, TaskPriority, StartPlanningResult } from "@/types/task";
+import type { TaskKind } from "@/types/note";
+
+// Issues + Systems write-only fields accepted by the task create/update API.
+// `kind` selects work/plan/issue; system_ids / arose_from_id are not mirrored
+// 1:1 on the Task model (the read side exposes `systems` + `arose_from_id`).
+interface IssueFields {
+  kind?: TaskKind;
+  system_ids?: number[];
+  arose_from_id?: number | null;
+}
 
 // Single-task + mutation surface. The list/filter/sort/pagination surface that
 // backed the removed /tasks list view was dropped in the 2026-06-02 drift-audit
@@ -34,7 +44,7 @@ export const useTasksStore = defineStore("tasks", () => {
     milestone_id?: number | null;
     parent_id?: number | null;
     recurrence_rule?: Record<string, unknown> | null;
-  }): Promise<Task> {
+  } & IssueFields): Promise<Task> {
     try {
       return await apiPost<Task>("/api/tasks", data);
     } catch (e) {
@@ -47,7 +57,7 @@ export const useTasksStore = defineStore("tasks", () => {
     id: number,
     data: Partial<
       Pick<Task, "title" | "body" | "tags" | "status" | "priority" | "due_date" | "project_id" | "milestone_id" | "parent_id" | "recurrence_rule">
-    >
+    > & IssueFields
   ): Promise<Task> {
     try {
       const task = await apiPut<Task>(`/api/tasks/${id}`, data);