View a policy version's content, and make policy text readable

The Policies admin page listed versions but never showed what any of them
said, so revising a policy meant retyping it blind into an empty draft box.
Each version row now has a View action that renders that version's text on
the page, editable in place. A draft is saved back to itself; editing a
published or archived version branches a new draft and leaves the original
alone, because acceptances are recorded against policy_version_id and text a
student agreed to must stay exactly as they saw it.

That viewer also exposed why a studio reported the acceptance box as
unreadable — one squashed line, overlapping words, a horizontal scrollbar.
Bodies are typed into a bare textarea, so most carry no markup, and the raw
text was emitted with its blank lines intact but nothing to turn them into
paragraphs. PolicyVersion::bodyHtml() now renders every body the way
WordPress renders post content (kses, then wpautop) and feeds all three
consumers: the booking/enrolment JSON, the signup form, and the new viewer.
Bodies written with markup are unaffected.

The other half was that .us-policy-body had no CSS whatsoever and inherited
whatever the theme did with an unstyled block in a form. It is now a bounded
reading box that scrolls vertically and breaks long tokens, so a pasted URL
cannot force the page sideways and a long policy cannot push the accept
checkbox out of view. RegistrationPage was also never enqueueing the plugin
stylesheet, which is why the signup gate looked worst of all.

Closes #126
Closes #127

Co-Authored-By: Claude Opus 5 <[email protected]>

src/Policy/PolicyVersion.php

@@ -42,6 +42,19 @@ class PolicyVersion {
 		return self::STATUS_PUBLISHED === $this->status;
 	}
 
+	/**
+	 * The body as display-ready HTML.
+	 *
+	 * Policy bodies are typed into a plain textarea, so most are written as
+	 * blank-line-separated prose with no markup at all — dropped into a page
+	 * as-is that collapses into one unreadable run of text. Running the same
+	 * `wpautop()` WordPress applies to post content turns those breaks into
+	 * paragraphs, and leaves bodies that do carry markup alone.
+	 */
+	public function bodyHtml(): string {
+		return wpautop( wp_kses_post( (string) $this->body ) );
+	}
+
 	/**
 	 * Returns a plain array representation of the version.
 	 *