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/server/src/common/decorators/auth-provenance.decorator.ts

@@ -1,4 +1,5 @@
 import { createParamDecorator, ExecutionContext } from '@nestjs/common';
+import { ProvenanceSource } from '../../core/auth/dto/jwt-payload';
 
 /**
  * The agent-edit provenance carried by the request, read from the SIGNED access
@@ -8,7 +9,7 @@ import { createParamDecorator, ExecutionContext } from '@nestjs/common';
  * cannot fake an 'agent' marker.
  */
 export interface AuthProvenanceData {
-  actor: 'user' | 'agent';
+  actor: ProvenanceSource;
   aiChatId: string | null;
 }