tool-call id uniquifier: the Lacan fix (owner-approved 2026-10-04)

DeepSeek via OpenRouter returns tool-call ids that reset every response —
a one-call-per-turn session names every call call_0. Everything keys on
toolCallId (the fold's call↔result join, the pending gate, answer
routing, the option-shuffle seed), so the Lacan session corrupted: the
quiz answer overwrote the ask card, the ask question vanished, and the
order scrambled. Record itself was always intact.

- src/server/pi/call-ids.ts (new): ToolCallIdUniquifier at the wire
  boundary — colliding ids remint once (orig~2, ~3…), the same mints at
  settlement; tables key by message OBJECT IDENTITY (streaming messages
  carry no ids; the message_end object is reference-identical to the
  state object). History never rewrites; providers see paired ids, which
  is protocol-legal (pi synthesizes ids for providers that send none).
- ui-stream: runPiTurn remaps events + settles through the uniquifier
  (spec.usedToolCallIds, seeded by chat-handler from the record).
- view.ts: findToolPart scans newest-first — pre-fix duplicate-id
  records (the existing Lacan session) heal on next render.
- tests: 9 unit pins (call-ids.test.ts) + the two-call_0 e2e (chat-flow):
  ask answered as ask, quiz as quiz, ids unique in the record.

src/server/chat-handler.ts

@@ -17,6 +17,7 @@ import {
 	unregisterLiveAgent,
 } from "./jobs.ts";
 import { piTurnResponse, runPiTurn } from "./pi/ui-stream.ts";
+import { collectToolCallIds } from "./pi/call-ids.ts";
 import { effectiveSettings, stores } from "./stores.ts";
 import { searchAvailable, searchProvider } from "./search.ts";
 import { providerKeyPresent } from "./keys.ts";
@@ -379,6 +380,12 @@ export async function handleChatInput(
 		registerLiveAgent(chatId, constructed);
 		const handle = runPiTurn({
 			agent: constructed,
+			// THE LACAN FIX (2026-10-04): seed the uniquifier with every
+			// tool-call id the record already holds — a provider that resets
+			// ids per response (DeepSeek) then gets fresh unique ids for this
+			// turn's calls at the wire boundary, on the wire, in the record,
+			// and in the next turn's context alike.
+			usedToolCallIds: new Set(collectToolCallIds(merged)),
 			// Stream-level failures are provider/transport internals — masked,
 			// like the SDK defaults. Tool-input validation messages never
 			// route through here: they ride the error-result path and reach the