refactor(chat): route browser chat through one runtime (P3 Slice-Zero Task 5) (#1172)

Co-authored-by: shaggy <[email protected]>

apps/gateway/src/chat/chat.dto.ts

@@ -1,5 +1,14 @@
 import type { ChannelAttachmentDto } from '@mosaicstack/types';
-import { IsOptional, IsString, IsUUID, MaxLength } from 'class-validator';
+import { Transform, Type } from 'class-transformer';
+import {
+  IsNotEmpty,
+  IsObject,
+  IsOptional,
+  IsString,
+  IsUUID,
+  MaxLength,
+  ValidateNested,
+} from 'class-validator';
 
 export class ChatRequestDto {
   @IsOptional()
@@ -37,3 +46,56 @@ export class ChatSocketMessageDto {
   /** Validated channel attachment references; binary content is not embedded. */
   attachments?: readonly ChannelAttachmentDto[];
 }
+
+/**
+ * Task Five, group 2 — the frozen pi-rpc `turn:send` selection triple.
+ *
+ * Each id is a required, non-empty, bounded string. There is no `@IsOptional` and no extra
+ * field: under `forbidNonWhitelisted` an unknown selection key is rejected, and a missing id
+ * fails `@IsString` (undefined is not a string) rather than silently passing.
+ */
+export class HarnessTurnSelectionDto {
+  @IsString()
+  @IsNotEmpty()
+  @MaxLength(255)
+  harnessId!: string;
+
+  @IsString()
+  @IsNotEmpty()
+  @MaxLength(255)
+  providerId!: string;
+
+  @IsString()
+  @IsNotEmpty()
+  @MaxLength(255)
+  modelId!: string;
+}
+
+/**
+ * Task Five, group 2 — the frozen wire contract for a pi-rpc `turn:send`.
+ *
+ * Validated through the production `ValidationPipe({ whitelist, forbidNonWhitelisted, transform })`:
+ * a UUID conversation id; `content` trimmed then bounded to 1..10_000 characters (whitespace-only
+ * collapses to empty and fails `@IsNotEmpty`); a nested `selection` object recursed with an
+ * explicit `@Type` (a bare `@ValidateNested` is masked green by class-validator's empty-metadata
+ * `unknownValue`); and a UUID-v4 idempotency key. No `provider`/`modelId`/`attachments` or other
+ * authority field is declared, so `forbidNonWhitelisted` rejects every unknown top-level key.
+ */
+export class HarnessTurnSendDto {
+  @IsUUID()
+  conversationId!: string;
+
+  @Transform(({ value }) => (typeof value === 'string' ? value.trim() : value))
+  @IsString()
+  @IsNotEmpty()
+  @MaxLength(10_000)
+  content!: string;
+
+  @IsObject()
+  @ValidateNested()
+  @Type(() => HarnessTurnSelectionDto)
+  selection!: HarnessTurnSelectionDto;
+
+  @IsUUID('4')
+  idempotencyKey!: string;
+}