Use short, readable share links for built-in movements

Sharing an unedited example produced a base64 blob of the whole document in
the URL (e.g. #doc=cG9zZWNvZGUgZXhlcmNpc2Ug...). Add a thin wrapper around
posecode-share (which stays preset-agnostic, since posecode-embed and
posecode-mcp use it too) that prefers a movement's short id when the source
matches a known preset exactly: #doc=squat. Anything edited or custom still
falls back to the full encoded token, and old-style base64 links keep working
unchanged. Wired into the share button, landing page example cards, and the
generated movement pages' "open in playground" links.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01B7RkyiTt9soiYdw5vt6BEP

Author: claude

playground/public/moves/arm-circles.html

@@ -124,7 +124,7 @@ <h1>Arm circles</h1>
         that LLMs like ChatGPT, Claude, and Gemini can write to describe human movement as text.
         Every joint angle below is hard-clamped to a safe range of motion.</p>
 
-      <a class="btn" href="/play.html#doc=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">▶ Open Arm circles in the playground →</a>
+      <a class="btn" href="/play.html#doc=arm-circles">▶ Open Arm circles in the playground →</a>
 
       <h2>How to do it</h2>
       <ol class="steps">

playground/public/moves/bent-over-row.html

@@ -124,7 +124,7 @@ <h1>Bent-over row</h1>
         that LLMs like ChatGPT, Claude, and Gemini can write to describe human movement as text.
         Every joint angle below is hard-clamped to a safe range of motion.</p>
 
-      <a class="btn" href="/play.html#doc=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">▶ Open Bent-over row in the playground →</a>
+      <a class="btn" href="/play.html#doc=bent-over-row">▶ Open Bent-over row in the playground →</a>
 
       <h2>How to do it</h2>
       <ol class="steps">

playground/public/moves/biceps.html

@@ -124,7 +124,7 @@ <h1>Biceps curl</h1>
         that LLMs like ChatGPT, Claude, and Gemini can write to describe human movement as text.
         Every joint angle below is hard-clamped to a safe range of motion.</p>
 
-      <a class="btn" href="/play.html#doc=cG9zZWNvZGUgZXhlcmNpc2UgIkJpY2VwcyBjdXJsIgogIHJpZyBodW1hbm9pZAogIHBvc2Ugc3RhcnQgPSBzdGFuZGluZwoKICBzdGVwICJDdXJsIiAxLjFzIGVhc2Utb3V0OgogICAgZWxib3dzOiBmbGV4IDEzNQogICAgY3VlICJDdXJsIHVwLCBrZWVwIHRoZSBlbGJvd3MgdHVja2VkIGF0IHlvdXIgc2lkZXMiCgogIHN0ZXAgIkxvd2VyIiAxLjRzIGVhc2UtaW46CiAgICBlbGJvd3M6IGZsZXggMTUKICAgIGN1ZSAiTG93ZXIgdW5kZXIgY29udHJvbDogZG9uJ3Qgc3dpbmciCgogIHJlcGVhdCAxMAo">▶ Open Biceps curl in the playground →</a>
+      <a class="btn" href="/play.html#doc=biceps">▶ Open Biceps curl in the playground →</a>
 
       <h2>How to do it</h2>
       <ol class="steps">

playground/public/moves/bicycle-crunch.html

@@ -124,7 +124,7 @@ <h1>Bicycle crunch</h1>
         that LLMs like ChatGPT, Claude, and Gemini can write to describe human movement as text.
         Every joint angle below is hard-clamped to a safe range of motion.</p>
 
-      <a class="btn" href="/play.html#doc=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">▶ Open Bicycle crunch in the playground →</a>
+      <a class="btn" href="/play.html#doc=bicycle-crunch">▶ Open Bicycle crunch in the playground →</a>
 
       <h2>How to do it</h2>
       <ol class="steps">

playground/public/moves/bow.html

@@ -124,7 +124,7 @@ <h1>Standing bow</h1>
         that LLMs like ChatGPT, Claude, and Gemini can write to describe human movement as text.
         Every joint angle below is hard-clamped to a safe range of motion.</p>
 
-      <a class="btn" href="/play.html#doc=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">▶ Open Standing bow in the playground →</a>
+      <a class="btn" href="/play.html#doc=bow">▶ Open Standing bow in the playground →</a>
 
       <h2>How to do it</h2>
       <ol class="steps">

playground/public/moves/box-squat.html

@@ -124,7 +124,7 @@ <h1>Box squat</h1>
         that LLMs like ChatGPT, Claude, and Gemini can write to describe human movement as text.
         Every joint angle below is hard-clamped to a safe range of motion.</p>
 
-      <a class="btn" href="/play.html#doc=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">▶ Open Box squat in the playground →</a>
+      <a class="btn" href="/play.html#doc=box-squat">▶ Open Box squat in the playground →</a>
 
       <h2>How to do it</h2>
       <ol class="steps">

playground/public/moves/box-step-taps.html

@@ -124,7 +124,7 @@ <h1>Box step taps</h1>
         that LLMs like ChatGPT, Claude, and Gemini can write to describe human movement as text.
         Every joint angle below is hard-clamped to a safe range of motion.</p>
 
-      <a class="btn" href="/play.html#doc=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">▶ Open Box step taps in the playground →</a>
+      <a class="btn" href="/play.html#doc=box-step-taps">▶ Open Box step taps in the playground →</a>
 
       <h2>How to do it</h2>
       <ol class="steps">

playground/public/moves/box-step.html

@@ -124,7 +124,7 @@ <h1>Box step</h1>
         that LLMs like ChatGPT, Claude, and Gemini can write to describe human movement as text.
         Every joint angle below is hard-clamped to a safe range of motion.</p>
 
-      <a class="btn" href="/play.html#doc=cG9zZWNvZGUgZXhlcmNpc2UgIkJveCBzdGVwIgogIHJpZyBodW1hbm9pZAogIHBvc2Ugc3RhcnQgPSBzdGFuZGluZwoKICBzdGVwICJTdGVwIGZvcndhcmQtcmlnaHQiIDAuOXMgZWFzZS1pbi1vdXQ6CiAgICBoaXBfcmlnaHQ6IGZsZXggMzUKICAgIGtuZWVfcmlnaHQ6IGZsZXggNDAKICAgIHNob3VsZGVyX2xlZnQ6IGZsZXggMjUKICAgIHNob3VsZGVyX3JpZ2h0OiBleHRlbmQgMTUKICAgIHRyYXZlbDogLTAuMzUgMC4zNQogICAgZ3JvdW5kLWxvY2s6IGZlZXQKICAgIGN1ZSAiU3RlcCB0aGUgcmlnaHQgZm9vdCBmb3J3YXJkIGFuZCBvdXQgdG8gdGhlIGNvcm5lciIKCiAgc3RlcCAiQ2xvc2UgdGhlIGZlZXQiIDAuN3MgZWFzZS1pbi1vdXQ6CiAgICBoaXBfcmlnaHQ6IGZsZXggMAogICAga25lZV9yaWdodDogZmxleCAwCiAgICBzaG91bGRlcnM6IGZsZXggMAogICAgdHJhdmVsOiAtMC4zNSAwLjM1CiAgICBncm91bmQtbG9jazogZmVldAogICAgY3VlICJCcmluZyB0aGUgbGVmdCBmb290IHRvIG1lZXQgaXQsIHN0YW5kaW5nIHRhbGwgb24gdGhlIGNvcm5lciIKCiAgc3RlcCAiU3RlcCBiYWNrLWxlZnQiIDAuOXMgZWFzZS1pbi1vdXQ6CiAgICBoaXBfbGVmdDogZmxleCAzNQogICAga25lZV9sZWZ0OiBmbGV4IDQwCiAgICBzaG91bGRlcl9yaWdodDogZmxleCAyNQogICAgc2hvdWxkZXJfbGVmdDogZXh0ZW5kIDE1CiAgICB0cmF2ZWw6IDAgMAogICAgZ3JvdW5kLWxvY2s6IGZlZXQKICAgIGN1ZSAiU3RlcCB0aGUgbGVmdCBmb290IGJhY2sgdG8gdGhlIHN0YXJ0IG9uIHRoZSBkaWFnb25hbCIKCiAgc3RlcCAiQ2xvc2UgaG9tZSIgMC43cyBlYXNlLWluLW91dDoKICAgIGhpcF9sZWZ0OiBmbGV4IDAKICAgIGtuZWVfbGVmdDogZmxleCAwCiAgICBzaG91bGRlcnM6IGZsZXggMAogICAgdHJhdmVsOiAwIDAKICAgIGdyb3VuZC1sb2NrOiBmZWV0CiAgICBjdWUgIkNsb3NlIHRoZSBmZWV0IHRvZ2V0aGVyLCBiYWNrIGhvbWUgYW5kIHJlYWR5IHRvIHJlcGVhdCIKCiAgcmVwZWF0IDQK">▶ Open Box step in the playground →</a>
+      <a class="btn" href="/play.html#doc=box-step">▶ Open Box step in the playground →</a>
 
       <h2>How to do it</h2>
       <ol class="steps">

playground/public/moves/calf-raise.html

@@ -124,7 +124,7 @@ <h1>Single-leg calf raise</h1>
         that LLMs like ChatGPT, Claude, and Gemini can write to describe human movement as text.
         Every joint angle below is hard-clamped to a safe range of motion.</p>
 
-      <a class="btn" href="/play.html#doc=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">▶ Open Single-leg calf raise in the playground →</a>
+      <a class="btn" href="/play.html#doc=calf-raise">▶ Open Single-leg calf raise in the playground →</a>
 
       <h2>How to do it</h2>
       <ol class="steps">

playground/public/moves/chair.html

@@ -124,7 +124,7 @@ <h1>Chair pose</h1>
         that LLMs like ChatGPT, Claude, and Gemini can write to describe human movement as text.
         Every joint angle below is hard-clamped to a safe range of motion.</p>
 
-      <a class="btn" href="/play.html#doc=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">▶ Open Chair pose in the playground →</a>
+      <a class="btn" href="/play.html#doc=chair">▶ Open Chair pose in the playground →</a>
 
       <h2>How to do it</h2>
       <ol class="steps">