Improve chat title generation and context compacting

public/css/shell.css

@@ -38,7 +38,7 @@ body.site-page { width:100%; max-width:none; margin:0; padding:0; background:var
 .chat-page .sidebar-workspace-card h2 { margin:0; font-size:.85rem; letter-spacing:0; font-family:var(--font-body); color:var(--text-soft); }
 .chat-page .chat-main { grid-template-rows:auto minmax(0,1fr) auto; }
 .chat-heading { min-width:0; }
-.chat-heading #workspaceNotice { margin:0; padding:10px 24px; border-width:0 0 1px; border-radius:0; font-size:.85rem; }
+.chat-heading #workspaceNotice { position:absolute; top:12px; right:16px; z-index:25; width:min(420px,calc(100% - 32px)); margin:0; padding:10px 14px; border-width:1px; border-radius:var(--radius-md); font-size:.85rem; box-shadow:var(--shadow-md); }
 .chat-page .chat-header { min-height:76px; }
 @media(max-width:1100px) { .shell-header { grid-template-columns:170px minmax(0,1fr) auto; gap:12px; padding:0 24px; }.shell-nav a { padding:0 10px; }.shell-username { max-width:90px; } }
 @media(max-width:980px) {