fix( gapic-generator-typescript): add .boolean() to diregapic and handwritten_layer

[quirogas]

This PR fixes a bug in the gapic-generator-typescript CLI wrapper where the diregapic and handwritten_layer flags were not explicitly marked as boolean in the yargs configuration.

Because these flags were missing the .boolean() call, yargs would treat them as requiring a value, causing them to consume the next positional argument (typically the first .proto file path). This led to generation failures or incomplete output when these flags were used via the CLI (e.g., in librarian generate).

Changes

• Updated core/generator/gapic-generator-typescript/typescript/src/gapic-generator-typescript.ts to add .boolean('diregapic') and .boolean('handwritten_layer').

For #5256

[gemini-code-assist]

Code Review

This pull request updates the GAPIC generator CLI configuration by explicitly marking the diregapic and handwritten_layer flags as boolean types. I have no feedback to provide.