refactor: remove passthrough() from zod schemas and make validation explicit

- Replace .passthrough() with explicit field definitions across all schemas
- Add missing optional fields (homeDir, happyHomeDir, happyLibDir, displayName)
- Refactor RawJSONLinesSchema to use structured base schema for clarity
- Improve schema validation strictness and type safety
- Update Machine interface to reflect explicit fields instead of index signature

cli/src/codex/utils/codexEventConverter.ts

@@ -6,7 +6,7 @@ const CodexSessionEventSchema = z.object({
     timestamp: z.string().optional(),
     type: z.string(),
     payload: z.unknown().optional()
-}).passthrough();
+});
 
 export type CodexSessionEvent = z.infer<typeof CodexSessionEventSchema>;