fix(chat): persist article conversations

[marcomarcogd]

Description

Persist article AI chat exchanges in the existing chat session tables so conversations remain accessible after creating a new conversation, switching sessions, or restarting the app.

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✅ Test addition/update

Related Issues

Fixes #1038

Changes Made

• Accept and validate the existing article/session context in AI chat requests.
• Save the user question before the provider call and retain it when the provider call fails.
• Save successful assistant responses and thinking content to the same session.
• Return the resolved session ID and history-save state without breaking older clients.
• Reload session history after success or failure and prevent session mutation while a request is running.
• Add stable ID tie-breakers to session and message ordering.
• Avoid logging endpoints, provider responses, prompts, or thinking content in the chat handler.

Testing

Test Configuration

• OS: macOS 15
• MrRSS Version: current main
• Go Version: 1.27
• Node Version: 24 for lint/build

Test Steps

1. Run GOCACHE=/private/tmp/mrss-chat-gocache go test -v -timeout=5m ./internal/database ./internal/handlers/chat.
2. Run cd frontend && npm run lint.
3. Run cd frontend && npm run build.
4. Run the existing article-operations Cypress spec and verify the new chat persistence case passes.

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• My changes generate no new warnings
• I have added tests that prove my fix is effective
• New and existing targeted backend tests pass locally
• Frontend lint and build pass locally
• This change has no dependent changes

Additional Notes

The new Cypress chat regression passed. Two pre-existing filter tests in the same spec did not find their UI labels in the browser-only harness; the remaining seven cases passed.

Breaking Changes

None. Requests without article_id continue to work without persistence.

[WCY-dt]

麻烦解决一下冲突

[marcomarcogd]

冲突已解决，已基于最新 release/v1.3.28@085e9ff 完成 rebase，官方 AI 搜索回归与聊天持久化回归均独立保留。新提交为 89a76b0c。本地 make check、前端 lint/单测/构建、相关 Go 测试及 macOS 构建均通过；相同 Test 工作流的 Backend、Frontend、Build、Skills 也已全部通过：https://github.com/marcomarcogd/MRSS/actions/runs/33030941332 。麻烦复审。