Tighten `hookSpecificOutput.hookEventName` schemas to the matching hook event

[sushichan044]

What issue are you seeing?

The generated hook command output JSON schemas currently allow hookSpecificOutput.hookEventName to be any value from the global hook event enum for several hook-specific output payloads.

For example, the pre-tool-use.command.output schema accepts any HookEventNameWire value for hookSpecificOutput.hookEventName, even though that hook-specific output is only valid for PreToolUse.

Affected output schemas:

• permission-request.command.output.schema.json
• post-tool-use.command.output.schema.json
• pre-tool-use.command.output.schema.json
• session-start.command.output.schema.json
• user-prompt-submit.command.output.schema.json

This makes the published schemas less precise than the runtime contract and can mislead external hook authors or schema-driven tooling into producing invalid combinations such as a PreToolUse hook-specific output with hookEventName: "PostToolUse".

What steps can reproduce the bug?

1. Inspect a generated hook command output schema such as codex-rs/hooks/schema/generated/pre-tool-use.command.output.schema.json.
2. Find properties.hookSpecificOutput.properties.hookEventName.
3. Observe that it references the global hook event enum instead of constraining the value to the matching hook event.

Current shape:

{
  "hookEventName": {
    "$ref": "#/definitions/HookEventNameWire"
  }
}

This permits unrelated hook event names inside an event-specific output payload.

What is the expected behavior?

Each hook-specific output schema should constrain hookSpecificOutput.hookEventName to the literal hook event name for that output type.

Expected shape:

{
  "hookEventName": {
    "const": "PreToolUse",
    "type": "string"
  }
}

The expected constants by schema are:

• permission-request.command.output.schema.json: PermissionRequest
• post-tool-use.command.output.schema.json: PostToolUse
• pre-tool-use.command.output.schema.json: PreToolUse
• session-start.command.output.schema.json: SessionStart
• user-prompt-submit.command.output.schema.json: UserPromptSubmit

This should match the existing pattern used by hook command input schemas, where hookEventName is already represented as an event-specific string constant.

Additional information

I already have a potential patch that fixes this issue in my computer.

[yui-stingray]

Checked this against current main (3936ed2). The generated output schemas still appear to have the mismatch described here: in the event-specific *.command.output.schema.json files, the referenced *HookSpecificOutputWire definition keeps hookEventName as a $ref to the global HookEventNameWire enum, while the matching input schemas already pin hook_event_name with an event-specific const.

A narrow regression test could assert that the generated output schemas for PermissionRequest, PostToolUse, PreToolUse, SessionStart, and UserPromptSubmit each emit the matching literal const for hookSpecificOutput.hookEventName, mirroring the existing input-schema shape.