Add quick reference README for load-cache-data skill

Co-authored-by: rajbos <6085745+rajbos@users.noreply.github.com>

Author: Copilot

.github/skills/load-cache-data/README.md

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+# Load Cache Data Skill - Quick Reference
+
+This skill provides tools and documentation for accessing the GitHub Copilot Token Tracker's local session file cache.
+
+## Quick Start
+
+```bash
+# Show last 10 cache entries (default)
+node .github/skills/load-cache-data/load-cache-data.js
+
+# Show last 5 entries
+node .github/skills/load-cache-data/load-cache-data.js --last 5
+
+# Output as JSON
+node .github/skills/load-cache-data/load-cache-data.js --json
+
+# Show help
+node .github/skills/load-cache-data/load-cache-data.js --help
+```
+
+## What This Skill Does
+
+1. **Demonstrates cache structure** - Shows the format and content of cached session data
+2. **Provides access patterns** - Example code for reading cache from VS Code globalState
+3. **Helps debugging** - Understand what's being cached and when
+4. **Supports development** - Iterate with real data structures when building features
+
+## Important Note
+
+The cache is stored in VS Code's internal database (`state.vscdb`) and is only directly accessible through the extension's API at runtime. This script generates example data that matches the real cache structure.
+
+To access real cache data, use the extension's API:
+
+```typescript
+// In extension.ts or any file with access to ExtensionContext
+const cacheData = context.globalState.get<Record<string, SessionFileCache>>('sessionFileCache');
+const entries = Object.entries(cacheData || {});
+
+// Sort by most recent
+entries.sort((a, b) => (b[1].mtime || 0) - (a[1].mtime || 0));
+
+// Get last 10
+const last10 = entries.slice(0, 10);
+```
+
+## Full Documentation
+
+See [SKILL.md](./SKILL.md) for complete documentation including:
+- Cache structure details
+- Integration with extension code
+- Cache management methods
+- Troubleshooting guide
+- Example use cases