fix(filters): browse with no rules works, popup under the input, no sticky headers (user report)

- Blank typed queries rode the STATIC autocomplete path for the classic
  six fields, where a single space similarity-matches into nothing —
  clicking an empty value box with no other filters said 'No matching
  values' in a library full of values. Blank = browse now always rides
  the composed engine (which trims and answers the top values); static
  keeps its pinned contract for real typed queries. Regression-pinned:
  browse with no rules lists the field's values.
- The value popup now drops BELOW the input (top: 100%), not over it.
- Field-menu group headers lost position:sticky — the search box alone
  stays pinned.

cmd/server/tests/filter_builder_test.go

@@ -526,6 +526,16 @@ func TestFilterSuggestionsUnderRules(t *testing.T) {
 	assert.NotContains(t, valuesOf(results), "spacewestern", "zero-match values never offered")
 	assert.NotContains(t, valuesOf(results), "history", "values outside the rules never offered")
 
+	// Browse with NO other rules in place: the blank query still lists
+	// the field's values (the static similarity path would answer a
+	// single space with nothing). Regression for the empty-browse bug.
+	status, results = suggest("genre", " ", "")
+	require.Equal(t, http.StatusOK, status)
+	assert.Contains(t, valuesOf(results), "fantasy", "browse with no rules lists the field's values")
+	status, results = suggest("author", " ", "")
+	require.Equal(t, http.StatusOK, status)
+	assert.Contains(t, valuesOf(results), "Amara Voss", "author browse with no rules")
+
 	// Library field menu: visibility-scoped, id values + name display
 	// (this test's fixture libraries are named "Test Builder Sug …").
 	status, results = suggest("library", "Test Builder", "")

internal/handlers/media.go

@@ -2648,9 +2648,14 @@ func (mh *MediaHandler) handleFieldValuesSearch(c *echo.Context, userID pgtype.U
 		tree = t
 	}
 
-	// Static path: the classic six with no rule tree (unchanged
-	// contract — the tag-dropdown island and deep links still ride it).
-	staticSix := tree == nil
+	// Static path: the classic six with a REAL typed query and no rule
+	// tree (unchanged contract — the tag-dropdown island and deep links
+	// still ride it). A BLANK typed query is BROWSE (the builder's
+	// click-the-box top-values list): the static queries would
+	// similarity-match a single space into nothing, so browse rides the
+	// composed engine, which trims the query and answers the top values
+	// under the rules.
+	staticSix := tree == nil && strings.TrimSpace(searchQuery) != ""
 	if staticSix {
 		switch fieldType {
 		case "author", "genre", "tags", "narrator", "series", "language":

web/static/input.css

@@ -1962,6 +1962,8 @@
   .fb-menu-value {
     width: 16rem;
     left: 0;
+    top: 100%;
+    margin-top: 0.25rem;
   }
   .fb-menu-group {
     font-size: 0.65rem;
@@ -1974,9 +1976,6 @@
     background-color: color-mix(in srgb, var(--text-primary) 5%, transparent);
     border-top: 1px solid var(--border);
     border-bottom: 1px solid var(--border);
-    position: sticky;
-    top: 0;
-    z-index: 1;
   }
   .fb-menu-filter-wrap {
     padding: 0.4rem 0.5rem;