Chat tabs, chat mode, own modes, compaction notice, CLI binaries again

- Terminals and file managers as tabs of a chat; chat terminals keep running on
  the server (no idle timeout) and re-attach from any device
- "Just chat" in New session and a built-in chat mode with a lean prompt and only
  web tools; custom modes with kind (coding/conversation), read-only and tool picker
- Mode selector as a dropdown
- The chat shows running compactions (automatic: tokens and share of the limit)
  and labels summaries
- Docker image builds and serves the terminal client binaries again
- Fix: atomic session updates; background title/usage writes no longer undo each
  other (auto compaction triggered one turn late)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/src/export.rs

@@ -53,7 +53,7 @@ pub fn markdown(s: &Session, messages: &[Message]) -> String {
         for p in &m.parts {
             match p {
                 Part::Text { text } => out.push_str(&format!("{}\n\n", text.trim())),
-                Part::Summary { text } => out.push_str(&format!("<details><summary>Summary of the earlier conversation</summary>\n\n{}\n\n</details>\n\n", text.trim())),
+                Part::Summary { text, .. } => out.push_str(&format!("<details><summary>Summary of the earlier conversation</summary>\n\n{}\n\n</details>\n\n", text.trim())),
                 Part::Reasoning { text, .. } if !text.trim().is_empty() => {
                     out.push_str(&format!("<details><summary>Thinking</summary>\n\n{}\n\n</details>\n\n", text.trim()))
                 }