Add workspaces, conversation sessions, app-managed computers and pictures

- Rail: Add icon with stacked form modals (bot, workspace, computer),
  coordinator, recent bots with "See all bots", Workspaces section, and
  a workspace mode listing only its crew
- Workspaces: page for context, bots (per-workspace instructions and
  memory), computers (default, link, unlink), models and delete;
  conversations scoped per bot per workspace
- Sessions: conversations split into searchable, reopenable sessions
  with carry-over summaries; sessions and new-session header icons
- Computers: created and provisioned over the docker socket, home dir
  kept at DATA_DIR/computers/<id> after delete; super admins only
- Models: workspace settings win over a bot's own, then the defaults
- Pictures for bots and workspaces; bots editable from the header
- Coordinator tools: update_workspace, set_bot_workspace_instructions

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/layouts/bots/(partials)/rail-section-add-button.tsx

@@ -0,0 +1,26 @@
+import Button from "@moduletrace/twui/layout/Button";
+import { Plus } from "lucide-react";
+
+type Props = {
+    title: string;
+    onClick: () => void;
+};
+
+/**
+ * The "+" beside a rail section's label.
+ */
+export default function RailSectionAddButton({ title, onClick }: Props) {
+    return (
+        <Button
+            title={title}
+            aria-label={title}
+            type="button"
+            variant="ghost"
+            color="text"
+            onClick={onClick}
+            className="size-6 p-0! rounded-default-sm text-ink-secondary dark:text-ink-secondary hover:text-ink hover:dark:text-ink hover:bg-sunken hover:dark:bg-sunken focus-visible:ring-2 focus-visible:ring-ink"
+        >
+            <Plus size={14} aria-hidden />
+        </Button>
+    );
+}