fix: support outputFromObservable() from @angular/core/rxjs-interop

[ashley-hunter]

Problem

Properties declared with `outputFromObservable()` from `@angular/core/rxjs-interop` were silently dropped from the compiled output metadata. The Angular runtime uses the `outputs: {}` object in `ɵɵdefineComponent`/`ɵɵdefineDirective` to wire up event bindings — missing entries mean parent components can never bind to those outputs.

Example that was broken:

readonly queryChanged = outputFromObservable(
  this.dataService.value$.pipe(
    skip(1),
    debounceTime(300),
  ),
);

Root cause

`try_parse_signal_output` in `property_decorators.rs` only matched the identifier `"output"`. `outputFromObservable` was never recognised, so its properties returned `None` and were excluded from the outputs metadata.

Fix

Extend `try_parse_signal_output` to detect both `output()` and `outputFromObservable()` (including namespaced forms like `core.outputFromObservable()`). The key behavioural difference is argument position: `output()` takes options at index 0, while `outputFromObservable(observable, options?)` takes them at index 1. The observable expression itself is irrelevant for metadata extraction and is ignored.

Tests

5 new unit tests added via TDD (red → green):

• Simple arg — `outputFromObservable(new EventEmitter())`
• Property reference — `outputFromObservable(this.service.obs$)`
• Piped observable — `outputFromObservable(this.dataService.value$.pipe(skip(1), debounceTime(300)))`
• Alias — `outputFromObservable(new EventEmitter(), { alias: 'clicked' })`
• Mixed — class using both `output()` and `outputFromObservable()` together

Each test uses normalized whitespace assertions to verify the exact `outputs:{}` structure inside `ɵɵdefineComponent`, plus insta snapshots locking the full compiled output.

Also adds an e2e compare fixture (`inputs-outputs/output-from-observable`) covering all four scenarios, verified against the official Angular compiler (100% pass).

Coverage

All 8 Angular initializer API functions are now handled by the Rust compiler. `outputFromObservable` was the only missing one.