feat(openapi): add x-fern-parameter-name support for websocket query parameters

[aditya-arolkar-swe]

Description

Refs: Slack thread from @aditya-arolkar-swe

Link to Devin run: https://app.devin.ai/sessions/2143d4e4bc654af4b7ca3d0aee402c1c

This PR adds support for the x-fern-parameter-name extension on websocket query parameters in AsyncAPI specs. Previously, this extension was only supported for HTTP endpoint parameters, and websocket query parameters always had parameterNameOverride set to undefined.

This enables users to rename websocket query parameters in generated SDKs to avoid naming conflicts (e.g., when a query parameter and an event type would generate the same property name).

Changes Made

• Updated parseAsyncAPIV2.ts to extract x-fern-parameter-name extension for websocket query parameters (both reference and non-reference schemas)
• Updated parseAsyncAPIV3.ts to extract x-fern-parameter-name extension for websocket channel parameters
• Added test fixture asyncapi-websocket-parameter-name to validate the feature

Testing

• Unit tests added (new test fixture with snapshots)
• Lint checks pass

Human Review Checklist

• Verify the extension extraction logic matches how it's done for HTTP parameters in convertParameters.ts
• Confirm both AsyncAPI v2 code paths (reference objects at line 186-189 and non-reference at line 212) are correctly updated
• Check that the generated Fern definition correctly uses name: field for overridden parameters (visible in snapshot at chat.yml)

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