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).

src/core/index.ts

@@ -31,13 +31,15 @@ export * from "./phases.ts";
 export * from "./pending.ts";
 export * from "./prompt-segments.ts";
 export * from "./math-delims.ts";
-export * from "./ui-message.ts";
 // Wave B (owner-approved 2026-09-26): the native record (LhMessage), the
-// one-way client-view projection, and the input-events contract — all
+// and the input-events contract — all
 // pure logic, browser-safe.
 export * from "./native-messages.ts";
-export * from "./projection.ts";
 export * from "./input-events.ts";
+// Wave D (owner-approved 2026-09-26): the client view model — the grouping
+// canon (one continuous assistant document, step separators) ported from
+// the deleted server projection to the client side. Pure, browser-safe.
+export * from "./view.ts";
 export * from "./tool-parts.ts";
 export * from "./prices.ts";
 export * from "./cost-summary.ts";