todo: group the url and query-string items into one theme

files-app becomes url-state: the file browser is where the work happened, but where
selection lives and who clears a query string are framework questions. The panel
framework's version of the same question moves in beside them, extracted from the
deep-read item, which keeps it as one of its three questions.

Item ids changed with the theme. Done now deliberately — no board reads them yet, and
this is the last cheap moment to move one.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

todo/workspaces-panels/a-deep-read-of-the-whole-framework-to.md

@@ -14,6 +14,9 @@ repeatedly, and nobody has since sat down and read the whole thing at once.
 Three questions to answer rather than assume: can the query strings come out of the flow; is there
 a better shape for panel-to-panel communication than the current channel/URL split; and what does
 the layout tree cost that a simpler one would not.
+The first of those now has its own item, `url-state/can-the-query-strings-come-out-of-the-flow`,
+filed with the file browser's work on the same question — that is where it has been thought about
+hardest. It stays part of this read; it is not a separate effort.
 **Fold the existing panel items into this** — the silent `key`/`appType` mismatch, the destructive
 layout migration on a renamed key, and `docs/workspace-panel-todo.md`. They are symptoms of the
 same unexamined design, and fixing them one at a time is how it stays unexamined.