movements: mark unreviewed ballet examples experimental (#91)

Demi-plié, Relevé, Tendu, and Chassé are ballet examples that have not been
reviewed by anyone with dance-domain knowledge. Per the dance UAT tracking
issue (#91) and its focused split #103, they must not be presented as
launch-ready until turnout, naming (Relevé vs Elevé), and step mechanics are
signed off by a reviewer.

Downgrade all four to 'experimental', which removes them from the generated
launch-ready movement gallery until reviewed. Ballroom steps (box step,
grapevine, waltz box) are unaffected and keep the Dance domain in the
gallery. Updates the library-ordering test to match.

Signed-off-by: Claude <noreply@anthropic.com>

Author: claude

playground/public/moves/box-step.html

@@ -212,7 +212,7 @@ <h2>The .posecode source</h2>
 </code></pre>
 
       <h2>More dance movements</h2>
-         <div class="chip-list"><a href="/moves/demi-plie.html">Demi-plié</a><a href="/moves/releve.html">Relevé</a><a href="/moves/tendu.html">Tendu</a><a href="/moves/grapevine.html">Grapevine (travels)</a><a href="/moves/waltz-box.html">Waltz box step</a><a href="/moves/chasse.html">Chassé (travels)</a></div>
+         <div class="chip-list"><a href="/moves/grapevine.html">Grapevine (travels)</a><a href="/moves/waltz-box.html">Waltz box step</a></div>
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