typescript: accept Deno wrapper syntax

[PerishCode]

Why

Flavor reported TypeScript parse errors for Deno wrapper syntax that Deno accepts in issue #48: inline object return types, intersection return types with inline objects, and for await loops.

Closes #48.

What

• Treat { ... } as an object or mapped type operand when parsing return types that also use { as the function body boundary.
• Accept optional await after for before the parenthesized loop header.
• Add parser regression coverage for the reported Deno wrapper syntax shapes.

Tests

• cargo fmt --all --check
• cargo clippy --locked --workspace --all-targets -- -D warnings
• cargo test --locked --workspace
• cargo test --locked -p flavor-plugin-typescript
• cargo run --locked -p flavor-cli -- check --root . --config flavor.toml