Core Rule Set: Ghost posts and code injection take a script element (closes #358)

While bodies are read, 941110 refused a `<script>` element in an HTML card
that embeds a widget, and in code injection that loads analytics. The new
exclusion 900366 switches 941110 off on the Admin API for `lexical`,
`mobiledoc` and `html` of posts and pages, their `codeinjection_head` and
`codeinjection_foot`, and settings `value`. Snippets, a newsletter's footer
and every other field and path still refuse it; `javascript:` links stay
refused everywhere.

Model: opus-5-5

SPEC.md

@@ -1792,11 +1792,20 @@ Code injection skips these rules:
 - 921130, 941100, 941160 and 941270, which refused `<meta>` and `<link>`
   elements.
 
-`<script>alert(1)</script>` and `javascript:alert(1)` are still refused in the
-articles and code injection (941110, 941170 and 941210). Path traversal and SQL
-injection are still refused in every field above. Script injection is too,
-outside the articles. `; wget http://example.com/x.sh` is still refused in the
-query fields, the plain text and the addresses.
+A `<script>` element skips 941110 in posts, pages and code injection, so an HTML
+card can embed a widget and code injection can load analytics. These are the
+fields, on the Admin API:
+
+- `lexical`, `mobiledoc` and `html` of posts and pages;
+- `codeinjection_head` and `codeinjection_foot` of posts and pages;
+- `value` of settings.
+
+`<script>alert(1)</script>` is still refused in snippets and newsletters.
+`javascript:alert(1)` is still refused in the articles and code injection
+(941170 and 941210). Path traversal and SQL injection are still refused in every
+field above. Script injection is too, outside the articles and code injection.
+`; wget http://example.com/x.sh` is still refused in the query fields, the plain
+text and the addresses.
 
 Coraza names a staff user's `profile_image` field `json.users.0.profile_image`.
 That name holds `.profile`, a file on the list of system files, so the name