feat(calls): "Call ended · 41 min · connection was good" toast (#143)

One line in the existing toast style when a call you were in ends: the
duration from our own join clock, plus the fork's io.lotus.call_summary
readout (fork ≥ 0.25.0-lotus.10) when it arrives — "connection was
good", "3 reconnects", "connection was poor for 4 min". Nothing is
stored or sent; the summary is one postMessage at hangup. Without the
fork summary the toast still shows the duration.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/utils/callSummary.test.ts

@@ -0,0 +1,67 @@
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import { describeCallDuration, describeCallEnd } from './callSummary';
+
+describe('describeCallDuration', () => {
+  it('picks the unit', () => {
+    assert.equal(describeCallDuration(40_000), '40 s');
+    assert.equal(describeCallDuration(41 * 60_000), '41 min');
+    assert.equal(describeCallDuration(65 * 60_000), '1 h 05 min');
+  });
+});
+
+describe('describeCallEnd', () => {
+  const min = 60_000;
+  it('without a summary shows just the duration', () => {
+    assert.equal(describeCallEnd(41 * min), 'Call ended · 41 min');
+  });
+  it('good / unknown', () => {
+    assert.equal(
+      describeCallEnd(41 * min, {
+        durationMs: 41 * min,
+        reconnects: 1,
+        poorMs: 0,
+        verdict: 'good',
+      }),
+      'Call ended · 41 min · connection was good',
+    );
+    assert.equal(
+      describeCallEnd(2 * min, {
+        durationMs: 2 * min,
+        reconnects: 0,
+        poorMs: 0,
+        verdict: 'unknown',
+      }),
+      'Call ended · 2 min',
+    );
+  });
+  it('reconnects and poor spells', () => {
+    assert.equal(
+      describeCallEnd(41 * min, {
+        durationMs: 41 * min,
+        reconnects: 3,
+        poorMs: 0,
+        verdict: 'fair',
+      }),
+      'Call ended · 41 min · 3 reconnects',
+    );
+    assert.equal(
+      describeCallEnd(12 * min, {
+        durationMs: 12 * min,
+        reconnects: 1,
+        poorMs: 4 * min,
+        verdict: 'poor',
+      }),
+      'Call ended · 12 min · 1 reconnect, connection was poor for 4 min',
+    );
+    assert.equal(
+      describeCallEnd(12 * min, {
+        durationMs: 12 * min,
+        reconnects: 0,
+        poorMs: 2_000,
+        verdict: 'fair',
+      }),
+      'Call ended · 12 min · connection was fair',
+    );
+  });
+});