fix(emcn): keep Prism grammar registrations in bundle, never throw on missing grammar

Consumers import { highlight, languages } from the @sim/emcn barrel, which
re-exported Prism's highlight straight from prismjs. Bundlers resolved that
passthrough directly from prismjs and skipped prism.ts's module body, dropping
the side-effect grammar registrations so languages.json (etc.) were undefined at
runtime. Prism then threw 'The language "json" has no grammar.', crashing the
start-block file[] input format field and every other workflow-editor code
highlighter.

Own highlight as a local wrapper so the registrations stay in the dependency
graph, and degrade to escaped plaintext when a grammar is missing instead of
throwing.

Author: waleedlatif1

packages/emcn/src/components/code/prism.ts

@@ -1,4 +1,4 @@
-import { highlight, languages } from 'prismjs'
+import { type Grammar, languages, highlight as prismHighlight } from 'prismjs'
 import 'prismjs/components/prism-javascript'
 import 'prismjs/components/prism-python'
 import 'prismjs/components/prism-json'
@@ -10,10 +10,32 @@ import 'prismjs/components/prism-json'
  * shared `Prism.languages` registry), which marks any module that statically
  * imports them as having side effects and therefore non-tree-shakeable. Keeping
  * them here — rather than in `code.tsx` — ensures Prism only enters bundles that
- * actually import `highlight`/`languages`, instead of every consumer of the
- * shared `@sim/emcn` barrel (which re-exports `Code`).
+ * actually import these utilities, instead of every consumer of the shared
+ * `@sim/emcn` barrel (which re-exports `Code`).
  *
  * `code.tsx` itself never imports this module statically; it loads it lazily via
  * dynamic `import()` on first highlight.
+ *
+ * `highlight` is a local wrapper rather than a re-export of Prism's `highlight`.
+ * A bare re-export lets bundlers resolve the binding straight from `prismjs` and
+ * skip this module's body, dropping the grammar registrations above so
+ * `languages.json` (etc.) become `undefined` at runtime. Owning the function
+ * keeps the registrations in the dependency graph and lets us degrade to escaped
+ * plaintext when a grammar is missing instead of throwing.
+ */
+
+function escapeHtml(text: string): string {
+  return text.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;')
+}
+
+/**
+ * Highlights `code` with the given Prism `grammar`, returning HTML markup.
+ * Falls back to escaped plaintext when `grammar` is undefined so a missing or
+ * unregistered language never throws `The language "<x>" has no grammar.`.
  */
+function highlight(code: string, grammar: Grammar | undefined, language: string): string {
+  if (!grammar) return escapeHtml(code)
+  return prismHighlight(code, grammar, language)
+}
+
 export { highlight, languages }