This PR adds support for named captures in the JavaScript templating API, allowing for more concise pattern matching and template generation.

Added optional `name` parameter to the `capture()` function, enabling inline named captures for cleaner rewrite rules.

### Key Changes

#### Named Captures Support

The `capture()` function now accepts an optional name parameter:

```typescript
// Inline named captures (new!)
pattern`${capture('left')} + ${capture('right')}`
template`${capture('right')} + ${capture('left')}`

// Unnamed captures (existing)
const left = capture();
const right = capture();
pattern`${left} + ${right}`
template`${right} + ${left}`
```

### Trade-offs

Slightly more verbose for rewrite rules:

```typescript
rewrite(() => ({
    before: pattern`${capture('left')} + ${capture('right')}`,
    after: template`${capture('right')} + ${capture('left')}`
}))
```

But enables direct literal string insertion:

```typescript
const type = 'Date';
template`${arg} instanceof ${type}`  // Generates: arg instanceof Date
```

This is valuable for common use cases where you want to insert variable code fragments.

### API Behavior

Template parameter types:
- `capture()` objects → Late binding via the values map (for pattern matching)
- Tree nodes → Direct AST substitution
- Strings/numbers/booleans → Inserted literally as code

The explicit `capture()` requirement makes the API more extensible for future enhancements while keeping common literal insertion cases simple.