[Report] Refactor Reporter Configuration for Type Safety and Extensibility

[priyanshus]

Currently, the reporters field in EvaliphyConfig accepts (string | any)[] | string, which is too permissive and lacks IDE discoverability. To align with "Strict Typing" principles, we need to restrict this to a set of supported reporter types. This will prevent configuration errors and provide a better developer experience through auto-completion.

Task: Implement a foundation which will be later evolved to excel/csv and other reporters.

The foundation should support:

• Console Reporter: Should be active by default.
• HTML Reporter: Should be easily toggled.
• Extensibility: The structure must allow for adding csv and excel formats in the near future without breaking changes.

Acceptance Criteria:

• Define a SupportedReporter union type (e.g., 'console' | 'html').
• Update EvaliphyConfig interface in packages/core/src/config/types.ts to use the new restricted types.
• Update the Zod schema in packages/core/src/config/schema.ts to validate these specific strings.
• Ensure mergeConfig logic handles the default state (e.g., ensuring console is always present or enabled).
• Verify that the reporter factory/registry can correctly resolve these literal types.
• Sufficient test coverage. Update e2e-tests.

Note: Please test your fix before raising PR. Don't blindly accept what LLM generates.

Describe the solution you'd like

export type BuiltInReporter = 'console' | 'html';

Describe alternatives you've considered

No response

Additional context

No response