feat(chat): live turn metrics — telemetry reducer + rendering

Consume wire/transport-contract 0.3.0 (step-complete event + timing
fields on usage/tool-result/done). Pure core/telemetry module:
foldMetricEvent (reducer) + derived selectors (stepTps, turnTps, etc).
TelemetryState is pure data, no active-turn tracking — consumers pass
turnId to selectors. ChatStore wires foldMetricEvent into handleDelta
and exposes telemetry + currentTurnId. ChatView shows step-metrics
footer (time/TPS/tokens) on assistant text bubbles and durationMs badge
on tool cards. New TurnSummary component renders turn-level stats
(wall-clock, tokens, steps, TPS) in a DaisyUI stats block. Extended
live-probe to verify telemetry events against bin/up (pending backend
restart). 336 tests, typecheck 0, biome clean, build ok.

1 files changed, 46 insertions, 0 deletions

diff --git a/src/features/chat/store.test.ts b/src/features/chat/store.test.ts
index 71781ac..347cdd7 100644
--- a/src/features/chat/store.test.ts
+++ b/src/features/chat/store.test.ts
@@ -393,6 +393,52 @@ describe("createChatStore", () => {
 		store.dispose();
 	});
 
+	it("folding step-complete and usage events populates telemetry", () => {
+		const transport = createFakeTransport();
+		const historySync = createFakeHistorySync();
+		const cache = createFakeCache();
+		const store = createChatStore({
+			conversationId: CONV_ID,
+			transport: transport.impl,
+			historySync: historySync.impl,
+			cache: cache.impl,
+		});
+
+		store.handleDelta(deltaEvent({ type: "turn-start", conversationId: CONV_ID, turnId: "t1" }));
+		store.handleDelta(
+			deltaEvent({
+				type: "step-complete",
+				conversationId: CONV_ID,
+				turnId: "t1",
+				stepId: "t1#0" as StepId,
+				ttftMs: 300,
+				decodeMs: 700,
+				genTotalMs: 1000,
+			}),
+		);
+		store.handleDelta(
+			deltaEvent({
+				type: "usage",
+				conversationId: CONV_ID,
+				turnId: "t1",
+				stepId: "t1#0" as StepId,
+				usage: { inputTokens: 50, outputTokens: 20 },
+			}),
+		);
+
+		const turn = store.telemetry.turns.get("t1");
+		expect(turn).toBeDefined();
+		expect(turn?.steps).toHaveLength(1);
+		const step = turn?.steps.find((s) => s.stepId === ("t1#0" as StepId));
+		expect(step).toBeDefined();
+		expect(step?.ttftMs).toBe(300);
+		expect(step?.decodeMs).toBe(700);
+		expect(step?.usage?.inputTokens).toBe(50);
+		expect(step?.usage?.outputTokens).toBe(20);
+
+		store.dispose();
+	});
+
 	it("handleDelta ignores a chat.delta for a different conversationId", () => {
 		const transport = createFakeTransport();
 		const historySync = createFakeHistorySync();