Wave D: native AgentEvent wire + client session rewrite (SDK purged)

Server: ui-stream.ts is verbatim pi AgentEvent passthrough (SSE data
lines + [DONE]); only app-level events are the loop-level error and
turn-settled terminal; onError carries raw provider text (owner ruling).

Client: useChat + the AI-SDK transport replaced by components/session-core.ts
(SessionModel: 409 identity-retry, optimistic c_ appends, absorbed()
adoption, needsContinuation, shared consume for POST + reattach) and the
session.ts hook; the golden-master grouping canon moved client-side into
core/view.ts (projectView); scanners read the native record (phaseAt3Lh,
danglingQuestionOf, graph toolParts, plan-blocks, runner, extraction).

Coverage: the native message is the unit (fork 3) with the call+result
inseparability bond rule; view-line-less messages (markers, error
results) are invisible to coverage and never checkpointed.

Deletes: chat-transport, projection, ui-message, their tests (ported to
tests/session-core.test.ts), and the ai + @ai-sdk/react dependencies —
the Vercel SDK is fully out of the tree. Wire pins in chat-flow rewritten
onto the AgentEvent dialect (eventsOf parser).

Gates: tsc clean, 994/994 tests, eslint clean, build green; live smoke
on PORT=3004 (verbatim wire → native record).

components/ai-elements/conversation.tsx

@@ -2,7 +2,7 @@
 
 import { Button } from "@/components/ui/button";
 import { cn } from "@/lib/utils";
-import type { UIMessage } from "ai";
+import type { LhViewMessage, LhViewPart } from "@/src/core";
 import { ArrowDownIcon, DownloadIcon } from "lucide-react";
 import type { ComponentProps } from "react";
 import { useCallback } from "react";
@@ -100,7 +100,7 @@ export const ConversationScrollButton = ({
   );
 };
 
-const getMessageText = (message: UIMessage): string =>
+const getMessageText = (message: LhViewMessage): string =>
   message.parts
     .filter((part) => part.type === "text")
     .map((part) => part.text)
@@ -110,21 +110,21 @@ export type ConversationDownloadProps = Omit<
   ComponentProps<typeof Button>,
   "onClick"
 > & {
-  messages: UIMessage[];
+  messages: LhViewMessage[];
   filename?: string;
-  formatMessage?: (message: UIMessage, index: number) => string;
+  formatMessage?: (message: LhViewMessage, index: number) => string;
 };
 
-const defaultFormatMessage = (message: UIMessage): string => {
+const defaultFormatMessage = (message: LhViewMessage): string => {
   const roleLabel =
     message.role.charAt(0).toUpperCase() + message.role.slice(1);
   return `**${roleLabel}:** ${getMessageText(message)}`;
 };
 
 export const messagesToMarkdown = (
-  messages: UIMessage[],
+  messages: LhViewMessage[],
   formatMessage: (
-    message: UIMessage,
+    message: LhViewMessage,
     index: number
   ) => string = defaultFormatMessage
 ): string => messages.map((msg, i) => formatMessage(msg, i)).join("\n\n");

components/ai-elements/message.tsx

@@ -15,9 +15,10 @@ import { cn } from "@/lib/utils";
 import { cjk } from "@streamdown/cjk";
 import { code } from "@streamdown/code";
 import { createMathPlugin } from "@streamdown/math";
-import type { UIMessage } from "ai";
+
 import { ChevronLeftIcon, ChevronRightIcon } from "lucide-react";
 import type { ComponentProps, HTMLAttributes, ReactElement } from "react";
+import type { LhViewMessage } from "@/src/core";
 import {
   createContext,
   memo,
@@ -36,7 +37,7 @@ import { mdComponents } from "@/components/md-blocks";
 import { transformMathDelimiters } from "@/src/core";
 
 export type MessageProps = HTMLAttributes<HTMLDivElement> & {
-  from: UIMessage["role"];
+  from: LhViewMessage["role"];
 };
 
 export const Message = ({ className, from, ...props }: MessageProps) => (