feat(render): rebuild typst render package cph-render (WU-2)

Single entry `display(info, target, parts)` over an ordered parts array, the
frozen contract the generated typst driver calls. Per-kind dispatch for
segment/example/lemma/sop; student/teacher matrix derived internally from
`target` (student hides example solution + lemma proof; teacher shows all).
Content-field values are consumed as already-evaluated content (driver
`include`s them ⇒ module body, ADR-0006), never imported/stringified. Optional
fields (lemma proof, example source) handled gracefully; unknown kind/target
degrade without crashing. Zero @preview deps (CI-robust); CJK + math styled.
Smoke compiles to non-empty student/teacher PDFs.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

render/src/elements/sop.typ

@@ -0,0 +1,19 @@
+// sop: a "standard operating procedure" — a methods/steps block.
+//
+// Contract fields:
+//   content: `sop` (required)
+//   scalar:  none
+//
+// Shown for all targets. Lightly boxed for visual separation; not numbered.
+
+#import "common.typ": element-box, tag-line, hue-of
+
+/// Render a sop part.
+#let display-sop(part, show-sop: true) = {
+  if show-sop {
+    element-box(hue-of.sop, {
+      tag-line[方法]
+      part.sop
+    })
+  }
+}