chore(comments): address PR #143 review (operator doc, badge test, dedup, type)

- [warn 1] Document the is_agent operator setup so it survives plan deletion:
  added an AI-agent block to .env.example (use a DEDICATED account, set is_agent
  via SQL, never flag a human/shared account) + a CHANGELOG "Added" entry.
- [warn 2] Test the badge deep-link side effects: ai-agent-badge.test.tsx now
  renders inside an explicit jotai store, clicks the badge, and asserts the
  active chat id, window-open, cleared draft, closed history modal, AND that
  stopPropagation keeps a parent onClick from firing.
- [suggestion 3] Hoist the window.matchMedia stub into vitest.setup.ts and drop
  the duplicated beforeAll block from the three test files (ai-agent-badge,
  comment-list-item, role-cards).
- [suggestion 4] Merge the two near-duplicate "non-clickable" cases via it.each.
- [follow-up 6] Introduce a single ProvenanceSource = 'user' | 'agent' type in
  jwt-payload.ts and reference it from AuthProvenanceData, JwtPayload/
  JwtCollabPayload, and resolveSource() — so a typo can't slip through as a bare
  string. (Server auth chain; client IComment mirroring left as a follow-up.)

Follow-up 5 (shared agentSourceFields write-stamp helper) is deferred as the
review marked it — the 6 REST sites use varied shapes (create-spread vs
resolve-conditional-null vs page move), so it's a separate focused refactor.

Tests: client badge/comment/role-cards suites 11/11 pass; server auth+comment
suites 62 pass; typecheck clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/client/src/features/comment/components/comment-list-item.test.tsx

@@ -1,24 +1,9 @@
-import { describe, it, expect, vi, beforeAll } from "vitest";
+import { describe, it, expect, vi } from "vitest";
 import { render, screen } from "@testing-library/react";
 import { MantineProvider } from "@mantine/core";
 import { IComment } from "@/features/comment/types/comment.types";
 
-// MantineProvider reads window.matchMedia on mount, which jsdom lacks.
-beforeAll(() => {
-  Object.defineProperty(window, "matchMedia", {
-    writable: true,
-    value: (query: string) => ({
-      matches: false,
-      media: query,
-      onchange: null,
-      addListener: vi.fn(),
-      removeListener: vi.fn(),
-      addEventListener: vi.fn(),
-      removeEventListener: vi.fn(),
-      dispatchEvent: vi.fn(),
-    }),
-  });
-});
+// matchMedia (read by MantineProvider) is stubbed globally in vitest.setup.ts.
 
 // The comment mutation hooks reach out to react-query/network — stub them so the
 // component renders in isolation. We only assert the AI-badge rendering branch.