a nav link carries only what it means

Pressing Layout while a band was open gave `?section=layout&band=footer`, so the row for the whole
section led to one part of it. Pressing a section carried whatever the last one had left behind.

Every link built a copy of the current query string and deleted the parameters known to be scoped —
`media`, then `page`, and `band` would have been the third. That is a list of exceptions that has to
grow every time a section gains a parameter, and it fails silently when somebody forgets: the link
still works, it just goes somewhere more specific than it says.

Starting from an empty query string inverts the default. A parameter survives a navigation only if the
link says so, which is one decision at each link rather than a list of everything that must not leak.

So a section row is `?section=x`, and a sub-item is that plus its own `band` or `page`. Nothing else
rides along, including the device and the open tab — both are restored to their defaults by the panel
that owns them, which is where a default belongs.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

web/NavPanel.tsx

@@ -66,29 +66,20 @@ export const NavPanel = () => {
 
     // Everything else in the URL is preserved. This is one screen of a workspace, and the global
     // query string carries state that belongs to the shell rather than to this panel.
-    const search = new URLSearchParams(params);
+    /*
+      A FRESH query string, carrying only the section.
+
+      It used to copy the current one and delete the parameters known to be scoped — `media`, then
+      `page`, and `band` would have been the third. That is a list of exceptions that has to grow every
+      time a section gains a parameter, and the failure is silent: pressing Layout while a band was open
+      gave `?section=layout&band=footer`, so the row for the whole section led to one part of it.
+
+      Starting empty inverts the default. A parameter survives a navigation only if the link SAYS so,
+      which is one decision at each link rather than a list of everything that must not leak.
+    */
+    const search = new URLSearchParams();
     search.set('section', section.key);
 
-    /*
-      `media` is Media's own folder, and it goes when you leave.
-
-      It survived every navigation, so `?section=home&media=GALLERY/CALAVERA+1` was an ordinary URL —
-      a parameter naming a folder in a section that is not open, carried into every link, and shared
-      or bookmarked that way. It is scoped to one section, so it is that section's to keep and nobody
-      else's to inherit.
-    */
-    if (section.key !== 'media') search.delete('media');
-
-    /*
-      `page` is Pages' own, and pressing PAGES ITSELF clears it.
-
-      Without this the section row and the row for whichever page was last open lead to the same
-      screen — the builder — and there is no way back to the list except the browser's back button.
-      Scoped like `media` above, and for the same reason: a parameter that belongs to one section
-      should not ride along into the others.
-    */
-    search.delete('page');
-
     /*
       `record` is dead and rides along in every URL until something removes it.
 
@@ -162,10 +153,10 @@ export const NavPanel = () => {
         <div key={section.key} className="flex flex-col">
           {row}
           {LAYOUT_BANDS.map((band) => {
-            const childSearch = new URLSearchParams(params);
+            // The section and this band, and nothing else — same rule as the section rows above.
+            const childSearch = new URLSearchParams();
             childSearch.set('section', 'layout');
             childSearch.set('band', band.key);
-            childSearch.delete('media');
 
             const current = active === 'layout' && params.get('band') === band.key;
 
@@ -192,10 +183,10 @@ export const NavPanel = () => {
       <div key={section.key} className="flex flex-col">
         {row}
         {pages.map((page) => {
-          const childSearch = new URLSearchParams(params);
+          // The section and this page, and nothing else.
+          const childSearch = new URLSearchParams();
           childSearch.set('section', 'pages');
           childSearch.set('page', pageParam(page));
-          childSearch.delete('media');
 
           const current = active === 'pages' && selectedPage === pageParam(page);