fix(di): resolve T | null constructor param types as injection tokens

[Brooooooklyn]

Summary

• Resolves issue DI: T | null constructor param types not narrowed for token resolution #285. @Optional() svc: MyService | null (and the bare svc: MyService | null variant) silently emitted ɵɵinvalidFactoryDep, which throws at instantiation — the canonical optional-DI pattern was unusable.
• Root cause: five copies of extract_param_token (component / directive / injectable / pipe / ng_module) plus two helpers in class_metadata/builders.rs only matched bare TSTypeReference. Any union annotation fell through to None.
• Adds shared helper util::resolve_di_token_type that mirrors Angular's typeReferenceToExpression in compiler-cli/src/ngtsc/reflection/src/typescript.ts — filters null keyword variants out of unions and narrows to the sole remaining type, transparently unwrapping TSParenthesizedType so (MyService | null), (MyService) | null, and MyService | (null) all resolve. undefined is intentionally preserved to keep T | undefined ambiguous, matching the reference.
• Threads the helper through all seven call sites.

Test plan

• 9 new regression tests across component / directive / injectable / pipe / ng_module — covering T | null, null | T, parenthesized forms, with and without @Optional().
• cargo test -p oxc_angular_compiler — 1044 lib tests pass (+ all integration tests).
• cargo run -p oxc_angular_conformance — 1252/1252 conformance cases pass.
• Pre-existing optional-DI tests (?: T suffix syntax) still pass; no behavior change for non-union annotations.
• Codex adversarial review caught a follow-up gap (parenthesized types) which is fixed in the same commit.

🤖 Generated with Claude Code

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Note

Medium Risk
Touches DI token resolution across all Angular decorator kinds and class metadata; behavior change is scoped to union/nullable annotations but incorrect narrowing could still mis-emit factory dependencies.

Overview
Fixes #285: constructor params typed as MyService | null (with or without @Optional()) no longer lose their injection token and emit ɵɵinvalidFactoryDep at runtime.

A shared resolve_di_token_type helper (aligned with Angular’s reference typeReferenceToExpression) strips null from unions, unwraps parenthesized types, and leaves T | undefined ambiguous. All extract_param_token paths (component, directive, injectable, pipe, ng_module) and class metadata type extraction now use it instead of matching only bare TSTypeReference.

Regression tests cover union order, optional vs non-optional, and parenthesized forms across decorator kinds.

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