fix: resolve all ESLint errors in Vue components

Fixed 22 ESLint errors across 26 Vue component files:
- Removed TypeScript type annotations from ReadingProgress.vue (converted to JS)
- Removed unused variables, imports, and duplicate function declarations
- Fixed HTML parsing errors (invalid attribute names, unclosed tags)
- Added missing :key directives to v-for loops
- Fixed duplicate object keys (backgroundImage)
- Replaced special characters in comments to avoid parsing issues
- Fixed malformed HTML tags (v-else", 003e attributes)

All warnings were left unchanged as requested. Build now passes with 0 errors.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

docs/.vitepress/theme/components/appendix/concurrency-models/AsyncAwaitDemo.vue

@@ -83,7 +83,7 @@
             </div>
 
             <div
-              v-for="(task, idx) in tasks"
+              v-for="task in tasks"
               :key="task.id"
               class="thread-row"
             >
@@ -165,7 +165,6 @@
 <script setup>
 import { ref, computed, watch } from 'vue'
 
-const comparisonMode = ref('memory')
 const coroutineCount = ref(1000)
 const isRunning = ref(false)
 const showDetails = ref(false)