feat(planning): warn of an overrun only past the displayed range

The expected wait sits near the middle of recent waits, so about half of
all runs pass it. Between the expected wait and the top of the range
shown before Calculate, the percentage now holds at 95% with no
remaining-time line; "Taking longer than expected" appears and is
announced only past that top.

Refs #300

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/services/planning-duration.service.spec.ts

@@ -220,7 +220,7 @@ describe('Indicative wait progress', () => {
 		});
 		expect(at(10_000)).toMatchObject({ percent: 47, overrun: false });
 		expect(at(19_999)).toMatchObject({ percent: 94, overrun: false });
-		expect(at(20_000)).toEqual({ percent: 95, remaining: null, overrun: true });
+		expect(at(20_000)).toEqual({ percent: 95, remaining: null, overrun: false });
 		expect(at(600_000)).toEqual({ percent: 95, remaining: null, overrun: true });
 		progress('complete');
 		expect(duration.wait()).toEqual({ percent: 100, remaining: null, overrun: false });
@@ -229,10 +229,25 @@ describe('Indicative wait progress', () => {
 	it('shows the remaining time only for expected waits of at least 3 seconds', () => {
 		start(2_999);
 		expect(at(1_000)).toEqual({ percent: 31, remaining: null, overrun: false });
-		expect(at(2_999)).toEqual({ percent: 95, remaining: null, overrun: true });
+		expect(at(2_999)).toEqual({ percent: 95, remaining: null, overrun: false });
 		resolve({ kind: 'PlanningIncomplete', completedStages: [], reasons: [] });
 	});
 
+	it.each([
+		[2_999, { minimum: 1, maximum: 9, unit: 'seconds' }, 9_000],
+		[20_000, { minimum: 10, maximum: 60, unit: 'seconds' }, 60_000],
+		[300_000, { minimum: 2, maximum: 15, unit: 'minutes' }, 900_000],
+	])(
+		'warns of an overrun of a %i ms expected wait only past the top of the range shown before Calculate',
+		(expectedMs, shown, topMs) => {
+			start(expectedMs);
+			expect(duration.estimate()).toEqual(shown);
+			expect(at(expectedMs)).toEqual({ percent: 95, remaining: null, overrun: false });
+			expect(at(topMs - 1)!.overrun).toBe(false);
+			expect(at(topMs)!.overrun).toBe(true);
+		},
+	);
+
 	it('rounds the remaining time to seconds, then 5-second steps, then minutes', () => {
 		start(3_000);
 		expect(at(0)!.remaining).toEqual({ value: 3, unit: 'seconds' });