Drop hardcoded section numbers from js_dsl example headings

`examples/js_dsl/mod.zig` and `mod.test.ts` label their sections with hardcoded numbers:

```zig
// ============================================================================
// Section 16: Static Class Fields
// ============================================================================
```

The numbering has already rotted — `mod.zig` jumps from 11 to 13 and from 13 to 15, so sections 12 and 14 were removed at some point without renumbering. The numbers carry no information the descriptive title doesn't already give, and they force churn (or drift) whenever a section is added or removed.

Raised in review on #76, where the new section was left unnumbered (`// Async Tasks`). That leaves the file inconsistent, so the remaining headings should follow.

**Scope:** strip the `Section N: ` prefix from the remaining headings in `examples/js_dsl/mod.zig` and `examples/js_dsl/mod.test.ts`, keeping the descriptive titles and the `====` rule lines. Comment-only; no test changes expected.