Add a New Webhook Event Handler

Follow these steps exactly. Do not skip any step.

Step 1: Write Failing Tests

Create test file tests/events/<handler-name>.test.ts with test cases for:

• Valid payload parsing
• Invalid payload rejection (returns err)
• Edge cases (system notes, ignored actions)

Run bun test to confirm the tests fail.

Step 2: Add Zod Schema

In src/events/parser.ts:

• Define the Zod schema for the new event payload
• Export the inferred TypeScript type

Step 3: Add Event Variant

In src/types/events.ts:

• Add a new variant to the WebhookEvent discriminated union:

``typescript | { readonly kind: "neweventname"; readonly payload: NewPayloadType } ``

Step 4: Update Parser

In src/events/parser.ts:

• Add a new parsing function (e.g., parseNewEventHook)
• Add the event type check to parseWebhookPayload

Step 5: Update Router

In src/events/router.ts:

• Add a new case to the switch (event.kind) block
• TypeScript will error until you handle the new variant (no default case)

Step 6: Verify

Run bun run check (typecheck + lint + test). All must pass.

Key Rules

• Every new event variant in the union MUST be handled in the router (exhaustive switch)
• Payloads MUST be validated through Zod schemas (never trust raw input)
• The parser function MUST return Result<WebhookEvent, AppError> (never throw)