fix(web): refine prompt anchor and sidebar branding

Replace the prompt timeline with a compact line index that expands to prompt-only navigation while keeping clear of the composer.

Use theme-specific Pythinker banners in the shared desktop sidebar and rebuild the committed web bundle.

Task: tasks/todo.md#prompt-anchor-redesign

Author: elkaix

.changeset/compact-prompt-anchor.md

@@ -0,0 +1,5 @@
+---
+"@pymodel/pythinker-code": patch
+---
+
+Make the chat prompt anchor a compact line index that expands to prompt labels.

.changeset/theme-sidebar-banners.md

@@ -0,0 +1,5 @@
+---
+"@pymodel/pythinker-code": patch
+---
+
+Use theme-matched Pythinker banners in the sidebar.

apps/pythinker-code/dist-web/.web-bundle-manifest.json

@@ -1,4 +1,4 @@
 {
-  "sourceHash": "b515297a2d3ed0f85c3a7e6c4960370e6e4c6eae60e6e92d1244a0d109b5320f",
-  "sourceFileCount": 402
+  "sourceHash": "7c44db902d1a4f2eaea0c303444679df09333a4eca33d9beccef0f67adf21a31",
+  "sourceFileCount": 404
 }