feat(maestro): open the bar from the sidebar search field

There is no ctrl-k on a phone and the web UI is mobile-first, so the field
the operator already reaches for becomes the touch entry point: focusing or
tapping it dispatches OPEN_COMMAND_BAR_EVENT and the shell opens the bar with
an empty query. The field is readonly and blurs itself first, so no keyboard
rises over it and the bar can be closed without reopening it.

This replaces the inline substring filter — one search affordance in the
header, not two. buildTree loses its filter argument, and the tree's "No
matches" empty state goes with it; the bar's own no-results state took over.
The filter's name-and-directory matching is now covered against the bar.

The bar's phone-width sheet moves to the spawn modal's 599px break, with
thumb-sized rows and a field that clears the zoom-on-focus threshold.

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

web/src/styles.css

@@ -1560,7 +1560,10 @@ input.leaf-rename:focus {
 }
 
 /* Phone: the bottom-sheet treatment the spawn modal already uses. */
-@media (max-width: 600px) {
+/* Bottom sheet at phone width, the same treatment (and the same 599px break)
+   the spawn modal uses: the bar is reached by thumb here, through the sidebar's
+   search field (#157), so it rides the bottom of the screen. */
+@media (max-width: 599px) {
   .cmdbar-overlay {
     grid-template-rows: 1fr auto;
     padding: 0;
@@ -1569,9 +1572,21 @@ input.leaf-rename:focus {
   .cmdbar-panel {
     grid-row: 2;
     width: 100%;
-    max-height: 70vh;
+    max-height: 70dvh;
     border-radius: var(--r-3) var(--r-3) 0 0;
     border-bottom: 0;
+    padding-bottom: env(safe-area-inset-bottom, 0px);
+  }
+
+  /* Thumb-sized rows and a field that clears the on-screen keyboard's
+     zoom-on-focus threshold (16px). */
+  .cmdbar-input {
+    font-size: var(--fs-17);
+    min-height: 44px;
+  }
+
+  .cmdbar-row {
+    min-height: 44px;
   }
 }