Move market composition from Python to .sx defcomps (Phase 3)

Python sxc/pages/ functions no longer build nested sx_call chains or
reference leaf component names. Instead they extract data (URLs, prices,
CSRF, cart state) and call a single top-level composition defcomp with
pure data values. The .sx defcomps handle all component-to-component
wiring, iteration (map), and conditional rendering.

New .sx composition defcomps:
- headers.sx: ~market-header-from-data, ~market-desktop-nav-from-data,
  ~market-product-header-from-data, ~market-product-admin-header-from-data
- prices.sx: ~market-prices-header-from-data, ~market-card-price-from-data
- navigation.sx: ~market-mobile-nav-from-data
- cards.sx: ~market-product-cards-content, ~market-card-from-data,
  ~market-cards-content, ~market-landing-from-data
- detail.sx: ~market-product-detail-from-data, ~market-detail-gallery-from-data,
  ~market-detail-info-from-data
- meta.sx: ~market-product-meta-from-data
- filters.sx: ~market-desktop-filter-from-data, ~market-mobile-chips-from-data,
  ~market-mobile-filter-content-from-data, plus 6 sub-composition defcomps

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

market/sx/headers.sx

@@ -15,3 +15,64 @@
      :class "px-2 py-1 text-stone-500 hover:text-stone-700"
      (i :class "fa fa-cog" :aria-hidden "true")))
 
+
+;; ---------------------------------------------------------------------------
+;; Composition defcomps — receive data, compose component trees
+;; ---------------------------------------------------------------------------
+
+;; Desktop category nav from pre-computed category data
+(defcomp ~market-desktop-nav-from-data (&key categories hx-select select-colours
+                                             all-href all-active admin-href)
+  (~market-desktop-category-nav
+    :links (<>
+      (~market-category-link :href all-href :hx-select hx-select
+         :active all-active :select-colours select-colours :label "All")
+      (map (lambda (cat)
+        (~market-category-link
+          :href (get cat "href") :hx-select hx-select
+          :active (get cat "active") :select-colours select-colours
+          :label (get cat "label"))) categories))
+    :admin (when admin-href
+      (~market-admin-link :href admin-href :hx-select hx-select))))
+
+;; Market-level header row from data
+(defcomp ~market-header-from-data (&key market-title top-slug sub-slug link-href
+                                        categories hx-select select-colours
+                                        all-href all-active admin-href oob)
+  (~menu-row-sx :id "market-row" :level 2
+    :link-href link-href
+    :link-label-content (~market-shop-label
+      :title market-title :top-slug (or top-slug "") :sub-div sub-slug)
+    :nav (~market-desktop-nav-from-data
+      :categories categories :hx-select hx-select :select-colours select-colours
+      :all-href all-href :all-active all-active :admin-href admin-href)
+    :child-id "market-header-child"
+    :oob oob))
+
+;; Product-level header row from data
+(defcomp ~market-product-header-from-data (&key title link-href hx-select
+                                                price-data admin-href oob)
+  (~menu-row-sx :id "product-row" :level 3
+    :link-href link-href
+    :link-label-content (~market-product-label :title title)
+    :nav (<>
+      (~market-prices-header-from-data
+        :cart-id (get price-data "cart-id")
+        :cart-action (get price-data "cart-action")
+        :csrf (get price-data "csrf")
+        :quantity (get price-data "quantity")
+        :cart-href (get price-data "cart-href")
+        :sp-val (get price-data "sp-val") :sp-str (get price-data "sp-str")
+        :rp-val (get price-data "rp-val") :rp-str (get price-data "rp-str")
+        :rrp-str (get price-data "rrp-str"))
+      (when admin-href
+        (~market-admin-link :href admin-href :hx-select hx-select)))
+    :child-id "product-header-child"
+    :oob oob))
+
+;; Product admin header row from data
+(defcomp ~market-product-admin-header-from-data (&key link-href oob)
+  (~menu-row-sx :id "product-admin-row" :level 4
+    :link-href link-href :link-label "admin!!" :icon "fa fa-cog"
+    :child-id "product-admin-header-child" :oob oob))
+