T23d: AI chat, conversations

- ConversationList: pinned first, then by day, newest first; a query keeps
  the titles that hold every word
- ConversationItem: a Tab stop when there is something to do; its menu of
  rename, pin and delete shows on hover, while open, or while the row holds
  focus; a press on the menu leaves the row shut
- new_chat_button, ProjectList, ProjectKnowledgePanel with a capacity meter
- SharedConversationView: who shared it and when, and a way to carry it on
- ConversationExport: format and thinking in a Dialog, Cancel or Export
- icons: square-pen, corner-down-right
- gallery: conversations with rename, pin and delete; projects; a shared
  conversation; export with a toast

src/chat/mod.rs

@@ -3,11 +3,13 @@ mod attach;
 mod cite;
 mod code;
 mod composer;
+mod conversations;
 mod list;
 mod media;
 mod message;
 mod params;
 mod play;
+mod projects;
 mod search;
 mod status;
 mod stream;
@@ -23,6 +25,7 @@ pub use attach::{Attachment, AttachmentChip, ContextChips};
 pub use cite::{CitationBadge, Source, SourceCard, SourceList};
 pub use code::CodeBlock;
 pub use composer::{AttachmentButton, DragDropOverlay, InputHint, PromptInput, SendButton};
+pub use conversations::{Conversation, ConversationItem, ConversationList, new_chat_button};
 pub use list::{DateSeparator, MessageList, ScrollToBottomButton};
 pub use media::{FileMessage, ImageGrid, ImageMessage, LinkPreviewCard};
 pub use message::{
@@ -30,6 +33,9 @@ pub use message::{
 };
 pub use params::{CostEstimator, Parameter, ParameterPanel, SystemPromptEditor, TokenCounter};
 pub use play::{AudioMessage, VideoMessage};
+pub use projects::{
+    ConversationExport, Project, ProjectKnowledgePanel, ProjectList, SharedConversationView,
+};
 pub use search::{DocumentChunkPreview, SearchProgress, StepState, WebResultCard};
 pub use status::{
     ErrorMessage, FeedbackForm, RateLimitNotice, ThinkingBlock, ThinkingDuration, ThinkingIndicator,