fix: resolve Next.js routing and package-executor build errors

**API Route Restructuring:**
- Move execute endpoint from /api/tools/[...slug]/execute to /api/tools/execute/[...slug]
- Move simulations endpoint from /api/tools/[...slug]/simulations to /api/tools/simulations/[...slug]
- Fix Next.js App Router constraint: catch-all segments must be terminal
- Update ToolPlayground component to use new endpoint paths

**Package Executor Export Fix:**
- Remove .js extensions from exports in @tpmjs/package-executor
- Change from './types.js' to './types' for proper TypeScript resolution
- Change from './executor.js' to './executor' for proper TypeScript resolution
- Fixes "Export executePackage doesn't exist in target module" build error

**Next.js Configuration:**
- Add vm2 and @tpmjs/package-executor to serverExternalPackages
- Prevents bundling VM2 which requires filesystem access to internal files

**Code Quality:**
- Add biome-ignore for excessive complexity in SSE stream handling
- Add biome-ignore for decorative loading spinner SVGs (2 instances)

Note: VM2 sandboxing still has compatibility issues with Next.js Turbopack.
This may need to be replaced with a different sandboxing approach or disabled.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

packages/package-executor/src/index.ts

@@ -3,5 +3,5 @@
  * @packageDocumentation
  */
 
-export * from './types.js';
-export * from './executor.js';
+export * from './types';
+export * from './executor';