Add an "Export chat" button to the AI agent chat window header that
downloads the active conversation as a Markdown file. The export is
client-only: it serializes the already-loaded persisted message rows
(no new network call, no server/DB change) and includes the request
internals the chat already holds — tool calls with their input/output,
per-message token usage, finish reason and error info.
- New util apps/client/src/features/ai-chat/utils/export-chat.ts:
buildChatMarkdown() + exportChatAsMarkdown(); reuses tool-parts
helpers so tool labels match the on-screen labels; fence() escapes
embedded code fences; slugify() yields a safe filename with a chatId
fallback; downloads via file-saver's saveAs.
- ai-chat-window.tsx: IconFileExport button in the header, shown only
for a saved chat with loaded rows (canExport); drag is unaffected.
- en-US: add "Export chat" and "You" i18n keys.
1968879fe5
