feat: Complete fleet — 94 skills across 10+ domains

Pulled ALL skills from 15 source repositories:
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- obra/superpowers: 14 (TDD, debugging, agents, planning)
- coreyhaines31/marketingskills: 25 (marketing, CRO, SEO, growth)
- better-auth/skills: 5 (auth patterns)
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- antfu/skills: 16 (Vue, Vite, Vitest, pnpm, Turborepo)
- Plus 13 individual skills from various repos

Mosaic Stack is not limited to coding — the Orchestrator and
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Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

skills/vue-best-practices/reference/transition-group-key-requirement.md

@@ -0,0 +1,107 @@
+---
+title: TransitionGroup Children Must Have Unique Keys
+impact: HIGH
+impactDescription: Missing or non-unique keys cause broken animations and Vue warnings
+type: gotcha
+tags: [vue3, transition-group, animation, key, v-for, list-animation]
+---
+
+# TransitionGroup Children Must Have Unique Keys
+
+**Impact: HIGH** - Unlike regular `<Transition>`, the `<TransitionGroup>` component **always requires** a unique `key` attribute on every child element. Without keys, Vue cannot track individual items, animations will break, and you'll see console warnings.
+
+This is a fundamental difference from `<Transition>` which works on single elements. Since `<TransitionGroup>` animates lists of elements, Vue needs keys to track which items are entering, leaving, or moving.
+
+## Task Checklist
+
+- [ ] Ensure every direct child of `<TransitionGroup>` has a unique `key` attribute
+- [ ] Use stable identifiers (IDs) rather than array indices for keys
+- [ ] Do not use the same key for different items at different times
+- [ ] When using `v-for`, always include `:key` binding
+
+**Incorrect - Missing keys:**
+```vue
+<template>
+  <!-- WRONG: Missing keys causes broken animations -->
+  <TransitionGroup name="list" tag="ul">
+    <li v-for="item in items">
+      {{ item.name }}
+    </li>
+  </TransitionGroup>
+</template>
+```
+
+**Incorrect - Using index as key:**
+```vue
+<template>
+  <!-- PROBLEMATIC: Index keys cause incorrect animations when list changes -->
+  <TransitionGroup name="list" tag="ul">
+    <li v-for="(item, index) in items" :key="index">
+      {{ item.name }}
+    </li>
+  </TransitionGroup>
+</template>
+```
+
+When using index as key:
+- If you remove item at index 2, what was index 3 becomes index 2
+- Vue thinks index 2 changed content rather than being removed
+- Animations fire on wrong elements
+
+**Correct - Unique stable keys:**
+```vue
+<template>
+  <!-- CORRECT: Unique ID keys for proper tracking -->
+  <TransitionGroup name="list" tag="ul">
+    <li v-for="item in items" :key="item.id">
+      {{ item.name }}
+    </li>
+  </TransitionGroup>
+</template>
+```
+
+**Correct - Keys on static children:**
+```vue
+<template>
+  <!-- CORRECT: Even static children need keys in TransitionGroup -->
+  <TransitionGroup name="fade" tag="div">
+    <span v-if="showA" key="a">Content A</span>
+    <span v-if="showB" key="b">Content B</span>
+    <span v-if="showC" key="c">Content C</span>
+  </TransitionGroup>
+</template>
+```
+
+## Common Error Messages
+
+Without keys, you'll see warnings like:
+```
+[Vue warn]: <TransitionGroup> children must be keyed.
+```
+
+## With Draggable Libraries
+
+When using `<TransitionGroup>` with libraries like `vue.draggable.next`, key issues can cause errors:
+
+```javascript
+// Error you might see without proper keys
+TypeError: domElement is null
+```
+
+Ensure all draggable items have unique keys:
+
+```vue
+<template>
+  <draggable v-model="items" item-key="id">
+    <template #item="{ element }">
+      <TransitionGroup name="list" tag="div">
+        <div :key="element.id">{{ element.name }}</div>
+      </TransitionGroup>
+    </template>
+  </draggable>
+</template>
+```
+
+## Reference
+- [Vue.js TransitionGroup](https://vuejs.org/guide/built-ins/transition-group.html)
+- [Vue.js List Rendering Keys](https://vuejs.org/guide/essentials/list.html#maintaining-state-with-key)