[10] feat(angular): extract template control flow

[fernandofielmann]

Goal

Represent Angular template control-flow constructs after template/component linkage is stable.

Scope

• Extract legacy structural directives such as *ngIf, *ngFor, and *ngSwitch where statically identifiable.
• Extract modern Angular blocks: @if, @for, and @switch.
• Preserve source ranges, branch/block kind, and nesting relationships.
• Associate referenced component members conservatively without evaluating template expressions.
• Avoid imposing runtime branch execution or collection cardinality.
• Use the bounded template extractor/grammar introduced by [09] feat(angular): link templates, selectors, and bindings #16.

Dependencies

• Depends on: [09] feat(angular): link templates, selectors, and bindings #16 ([09] template links, selectors, and bindings).
• Blocks: [14] cross-stack feature flags.

Acceptance criteria

• Legacy and modern control-flow syntax is represented with deterministic nesting.
• else, @else, @empty, and switch cases retain their structural association.
• Malformed or unsupported dynamic expressions do not crash indexing or create guessed edges.
• Inline and external templates behave equivalently.
• Sequential and parallel pipelines emit equivalent results.
• Graph schema and README document the control-flow representation.

Validation

• Add positive, negative, nested, malformed, mixed-syntax, and parity fixtures.
• Run Angular template/edge suites, lint-ci, and scripts/test.sh.