feat(content): extend chapters schema with route map + panel fields

Add cards[].href and cards[].cta for the landing route map's six cards
whose call-to-action text is not uniform (Open chapter / Open lab /
Open desk). Add sections[].panelLabel, panelCode, panelHint for the
highlighted rule panels on /models/, /agents/, /skills/. Add top-level
threadLabel / threadText / footer for the landing-page strip and the
chapter-page footer line. Both locales remain mandatory on every
localized field.

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

src/content/config.ts

@@ -92,9 +92,23 @@ const skillInstallPrompts = defineCollection({
   }),
 });
 
-// Chapter copy for /models/, /agents/, /skills/, /summary/. The body of
+// Chapter copy for /models/, /agents/, /skills/, /summary/ and the landing
-// each page composes one or more sections; the field names mirror what the
+// route map. The body of each page composes one or more sections; the
-// existing HTML already says aloud (eyebrow / lede / card titles).
+// field names mirror what the existing HTML already says aloud (eyebrow /
+// lede / card titles).
+//
+// `cards[].href` and `cards[].cta` were added in task 04b: the landing
+// route map's six cards have non-uniform call-to-action text (four read
+// "Open chapter →", one "Open lab →", one "Open desk →"), so a single
+// hard-coded default would be wrong. `href` is the destination; `cta` is
+// the localized link text.
+//
+// `sections[].panelLabel` / `panelCode` / `panelHint` carry the highlighted
+// rule panels on /models/, /agents/, and /skills/ (the routing rule, the
+// MAIN / ORCHESTRATOR tree, and the package-anatomy hint).
+//
+// `threadLabel` / `threadText` and `footer` carry the landing-page thread
+// strip and footer line.
 const chapters = defineCollection({
   type: 'data',
   schema: z.object({
@@ -102,12 +116,17 @@ const chapters = defineCollection({
     eyebrow: localized,
     title: localized,
     lede: localized,
+    threadLabel: localized.optional(),
+    threadText: localized.optional(),
+    footer: localized.optional(),
     cards: z
       .array(
         z.object({
           label: localized,
           title: localized,
           copy: localized,
+          href: z.string().optional(),
+          cta: localized.optional(),
         }),
       )
       .optional(),
@@ -117,6 +136,9 @@ const chapters = defineCollection({
           eyebrow: localized.optional(),
           title: localized,
           copy: localized.optional(),
+          panelLabel: localized.optional(),
+          panelCode: localized.optional(),
+          panelHint: localized.optional(),
           steps: z
             .array(
               z.object({