JavaScript: Add CaptureKind to template captures

[knutwannheden]

Summary

• Add CaptureKind enum (Expression, Identifier, TypeReference, Statement) to the JS templating engine, mirroring the C# CaptureKind added in C#: Add CaptureKind to template captures for position-aware scaffolding #7059
• Add kind-specific factory functions (expr(), ident(), typeRef(), stmt()) as alternatives to the generic capture(), available both as direct imports and namespace-qualified on capture (e.g. capture.expr())
• Migrate all existing templating tests to use the kind-specific factories, documenting the semantic intent of each capture
• Kind-specific factories delegate to capture() internally, so there is a single code path for name resolution and option handling

API

// Direct imports (concise)
import { expr, ident, typeRef, stmt } from './capture';
const e = expr('x');
const n = ident('method');
const t = typeRef('ret');
const s = stmt('body');

// Namespace-qualified (no collisions)
import { capture } from './capture';
capture.expr('x')
capture.ident('method')

// Backwards compatible
capture('x')  // defaults to Expression kind
capture({ name: 'x', kind: CaptureKind.Identifier })

Note

The CaptureKind metadata is stored on captures but not yet consumed by the engine — scaffold-aware placeholder generation will follow once we have concrete recipes that need different scaffold wrapping.

Test plan

• 18 new tests for capture kinds (enum values, factory functions, backwards compat, namespace access, any() integration, pattern usage)
• All 258 existing templating tests pass with migrated factory calls
• TypeScript typecheck passes with no new errors