Square off the rail header and add a back button

The rail header now sits in the standard 64px row with a hairline under
it, matching the pane headers, and shows the full logo off the chat
pages instead of the bare stone. A back button joins the conversation
and settings headers (workspace pages only for the conversation). The
rail's own back link and the dividers around it are switched off for now.

Also renames the bot and workspace Delete group to Danger Zone, lifts the
step budget to 50, and lets Logo render without its home link.

src/data/app-data.ts

@@ -240,7 +240,7 @@ export const AppData = {
     /**
      * Model turns in one text run before it must stop and report.
      */
-    HarnessMaxToolSteps: 30,
+    HarnessMaxToolSteps: 50,
     /**
      * Longest tool result handed back to the model.
      */
@@ -462,7 +462,8 @@ export const AppData = {
     /**
      * What a speech model reads when a voice is tried in the model settings.
      */
-    VoicePreviewText: "Hi there. This is how I'll sound when I read my replies aloud.",
+    VoicePreviewText:
+        "Hi there. This is how I'll sound when I read my replies aloud.",
     /**
      * Largest picture a bot or a workspace can have.
      */