Chat improvements (#22823)

* Add score fusion helpers for find_similar_objects chat tool

* Add candidate query builder for find_similar_objects chat tool

* register find_similar_objects chat tool definition

* implement _execute_find_similar_objects chat tool dispatcher

* Dispatch find_similar_objects in chat tool executor

* Teach chat system prompt when to use find_similar_objects

* Add i18n strings for find_similar_objects chat tool

* Add frontend extractor for find_similar_objects tool response

* Render anchor badge and similarity scores in chat results

* formatting

* filter similarity results in python, not sqlite-vec

* extract pure chat helpers to chat_util module

* Teach chat system prompt about attached_event marker

* Add parseAttachedEvent and prependAttachment helpers

* Add i18n strings for chat event attachments

* Add ChatAttachmentChip component

* Make chat thumbnails attach to composer on click

* Render attachment chip in user chat bubbles

* Add ChatQuickReplies pill row component

* Add ChatPaperclipButton with event picker popover

* Wire event attachments into chat composer and messages

* add ability to stop streaming

* tweak cursor to appear at the end of the same line of the streaming response

* use abort signal

* add tooltip

* display label and camera on attachment chip