feat(ui): ralpi-style chat progress and pipeline-overview footer

phases.ts becomes a live chat widget (spinner + tool-call tree) and the
check-runner posts per-agent tool-call summaries and an expandable
completion tree through a custom message renderer; footer.ts adds the
static pipeline-overview status strip for single checks and /pygienium-all.

tests/all.test.ts

@@ -355,4 +355,28 @@ describe("/pygienium-all orchestrator (task 12)", () => {
 		expect(joined).toContain("Beta");
 		expect(joined).toContain("all [");
 	});
+
+	it("renders only the unified widget in UI mode (no per-check spinner)", async () => {
+		registerCheck(fakeCheck("alpha"));
+		registerCheck(fakeCheck("beta"));
+		const calls: Array<[string, string[] | undefined]> = [];
+		const ui = {
+			setWidget: (key: string, content: string[] | undefined) => {
+				calls.push([key, content]);
+			},
+		} as never; // stub ExtensionUIContext (tests have no pi type imports)
+
+		await runAllChecks({ cwd, ui, hasUI: true });
+
+		const keys = new Set(calls.map(([k]) => k));
+		// The unified strip drives the widget area…
+		expect(keys.has("pygienium-all-progress")).toBe(true);
+		// …and per-check strips never claim it, so no second spinner can
+		// flicker/swap against the unified one.
+		expect(keys.has("pygienium-progress")).toBe(false);
+		// The widget is cleared when the run completes.
+		const last = calls[calls.length - 1]!;
+		expect(last[0]).toBe("pygienium-all-progress");
+		expect(last[1]).toBeUndefined();
+	});
 });