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).

package.json

@@ -17,7 +17,6 @@
 		"desktop:dist": "next build && node scripts/build-server.mjs && electron-builder --mac --arm64"
 	},
 	"dependencies": {
-		"@ai-sdk/react": "^4.0.79",
 		"@earendil-works/pi-agent-core": "^0.85.1",
 		"@earendil-works/pi-ai": "^0.85.1",
 		"typebox": "1.3.7",
@@ -29,7 +28,6 @@
 		"@streamdown/math": "^1.0.2",
 		"@streamdown/mermaid": "^1.0.2",
 		"@xyflow/react": "^12.11.3",
-		"ai": "^7.0.76",
 		"ansi-to-react": "^6.2.6",
 		"class-variance-authority": "^0.7.1",
 		"clsx": "^2.1.1",