feat(frontend): viewer humain fil-par-paire en lecture seule (LS7)

Frontend pur, lecture seule, consomme read_conversation_page (LS6) ; aucun changement backend.
- adapters : conversation.ts (gateway) + conversationNormalization.ts.
- features/conversations : useConversationThread, ConversationViewer, index.
- domain (types LS7), ports (port + Gateways.conversation), adapters/index, mock (+ clé inventaire).
- features/workstate : ProjectWorkStatePanel prop onOpenConversation.
- features/projects : ProjectsView swap viewer.
- tests (QA, verts) : conversationNormalization, mock/conversationGateway,
  useConversationThread, ConversationViewer, ProjectsView.ls7. tsc 0, vitest 443/443 (+36).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/domain/index.ts

@@ -213,6 +213,36 @@ export interface ProjectWorkState {
   conversations: ConversationWorkSummary[];
 }
 
+// ---------------------------------------------------------------------------
+// Conversation transcript (LS7 — human thread-per-pair viewer, mirror of LS6 DTO)
+// ---------------------------------------------------------------------------
+
+/** Nature of a transcript turn (mirror of the backend `TurnRole`). */
+export type TurnRole = "prompt" | "response" | "toolActivity";
+
+/** Origin of a transcript turn (mirror of the backend `TurnSource`). */
+export type TurnSource = { kind: "human" } | { kind: "agent"; agentId: string };
+
+/** One turn of the human transcript — full text, never truncated. */
+export interface TurnView {
+  id: string;
+  atMs: number;
+  role: TurnRole;
+  source: TurnSource;
+  text: string;
+  textLen: number;
+}
+
+/** Pagination travel direction (`"backward"` = towards older turns). */
+export type PageDirection = "forward" | "backward";
+
+/** A page of the human transcript, oldest-to-newest. */
+export interface TurnPage {
+  turns: TurnView[];
+  hasMore: boolean;
+  nextAnchor?: string;
+}
+
 // ---------------------------------------------------------------------------
 // Permissions (LP1)
 // ---------------------------------------------------------------------------