feat(week): day selection with URL-driven state

- weekKey and selectedDay driven by ?week=&?day= query params
- Bare /week canonicalizes via replaceState (adds week+day params)
- Chip clicks: replaceState (no history push, no scroll jump)
- Week prev/next: goto with history push (back/forward works)
- Default day when week changes: today if in week, else Monday
- Keyboard navigation: ArrowLeft/Right cycles through chips
- Selected chip scrolls into view on selection change
- DayDetail always rendered for selectedDay (not just today)
- detailCaps reactive on closedDaysMap — updates immediately after
  close/reopen/mark without extra load()
- Chips now wired: selected prop, onclick handler
- DayChip tabindex: 0 for selected chip, -1 for others (roving tabindex)

web/src/routes/week/+page.svelte

@@ -1,14 +1,73 @@
 <script lang="ts">
-	import { onMount } from 'svelte';
+	import { page } from '$app/stores';
+	import { goto } from '$app/navigation';
 	import { entries, days, weeks, settings, type Entry, type ClosedDay, type ClosedWeek, type Settings, ApiError } from '$lib/api/client';
 	import {
-		currentWeekKey, weekDayKeys, formatDurationShort, formatDelta, todayKey, isWorkday
+		currentWeekKey, weekDayKeys, formatDurationShort, formatDelta,
+		todayKey, isWorkday, dayCapabilities
 	} from '$lib/utils';
 	import DayChip from '$lib/components/DayChip.svelte';
 	import DayDetail from '$lib/components/DayDetail.svelte';
-	import { dayCapabilities } from '$lib/utils';
 
-	let weekKey = $state(currentWeekKey());
+	// ── URL-driven state ────────────────────────────────────────────────────────
+
+	// Canonical default day for a given week: today if in the week, else Monday.
+	function defaultDayForWeek(wk: string): string {
+		const keys = weekDayKeys(wk);
+		const t = todayKey();
+		return keys.includes(t) ? t : keys[0];
+	}
+
+	// Read week+day from URL; fall back to current week + default day.
+	let weekKey = $derived(
+		$page.url.searchParams.get('week') ?? currentWeekKey()
+	);
+	let selectedDay = $derived(
+		$page.url.searchParams.get('day') ?? defaultDayForWeek(weekKey)
+	);
+
+	// On mount: if URL is bare /week (no params), canonicalize via replaceState.
+	$effect(() => {
+		const url = $page.url;
+		if (!url.searchParams.has('week') || !url.searchParams.has('day')) {
+			const wk = url.searchParams.get('week') ?? currentWeekKey();
+			const dk = url.searchParams.get('day') ?? defaultDayForWeek(wk);
+			const next = new URL(url);
+			next.searchParams.set('week', wk);
+			next.searchParams.set('day', dk);
+			goto(next.toString(), { replaceState: true, noScroll: true, keepFocus: true });
+		}
+	});
+
+	function selectDay(dk: string) {
+		const next = new URL($page.url);
+		next.searchParams.set('day', dk);
+		goto(next.toString(), { replaceState: true, noScroll: true, keepFocus: true });
+	}
+
+	function navigateWeek(offset: number) {
+		const wk = offsetWeek(weekKey, offset);
+		const dk = defaultDayForWeek(wk);
+		const next = new URL($page.url);
+		next.searchParams.set('week', wk);
+		next.searchParams.set('day', dk);
+		// Push history so back/forward works for week navigation.
+		goto(next.toString(), { noScroll: true, keepFocus: true });
+	}
+
+	function offsetWeek(wk: string, offset: number): string {
+		const [y, w] = wk.split('-W').map(Number);
+		const date = new Date(y, 0, 4);
+		date.setDate(date.getDate() + (w - 1) * 7 + offset * 7);
+		const thu = new Date(date);
+		thu.setDate(date.getDate() + 4 - (date.getDay() || 7));
+		const ys = new Date(thu.getFullYear(), 0, 1);
+		const weekNum = Math.ceil(((thu.getTime() - ys.getTime()) / 86400000 + 1) / 7);
+		return `${thu.getFullYear()}-W${String(weekNum).padStart(2, '0')}`;
+	}
+
+	// ── Data ────────────────────────────────────────────────────────────────────
+
 	let dayKeys = $derived(weekDayKeys(weekKey));
 	let closedDaysMap = $state<Record<string, ClosedDay>>({});
 	let weekEntries = $state<Entry[]>([]);
@@ -38,6 +97,21 @@
 
 	$effect(() => { weekKey; load(); });
 
+	// ── Keyboard navigation for chip strip ──────────────────────────────────────
+
+	function handleStripKeydown(e: KeyboardEvent) {
+		const idx = dayKeys.indexOf(selectedDay);
+		if (e.key === 'ArrowRight' && idx < 6) {
+			selectDay(dayKeys[idx + 1]);
+			e.preventDefault();
+		} else if (e.key === 'ArrowLeft' && idx > 0) {
+			selectDay(dayKeys[idx - 1]);
+			e.preventDefault();
+		}
+	}
+
+	// ── Week actions ─────────────────────────────────────────────────────────────
+
 	async function handleCloseWeek() {
 		error = '';
 		try {
@@ -58,9 +132,10 @@
 		}
 	}
 
+	// ── Derived display values ───────────────────────────────────────────────────
+
 	const DAY_NAMES = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'];
 
-	// Per-day worked ms: use closed_days value if closed, else sum open entries.
 	function dayWorkedMs(dk: string): number {
 		const cd = closedDaysMap[dk];
 		if (cd) return cd.worked_ms;
@@ -69,7 +144,6 @@
 			.reduce((sum, e) => sum + (e.end_time! - e.start_time), 0);
 	}
 
-	// Daily expected ms for a workday; 0 for weekends.
 	function dailyExpectedMs(dk: string): number {
 		if (!currentSettings) return 0;
 		const mask = currentSettings.workdays_mask;
@@ -85,58 +159,50 @@
 		currentSettings ? currentSettings.hours_per_week * 3_600_000 : 0
 	);
 
-	// Track which day_keys have at least one entry (for close-week guard).
+	const daysWithEntries = $derived(new Set(weekEntries.map((e) => e.day_key)));
-	const daysWithEntries = $derived(
-		new Set(weekEntries.map((e) => e.day_key))
-	);
 
-	// Week can be closed if it's not already closed, the week has started,
-	// and every past workday that has entries is also closed.
 	const canCloseWeek = $derived(
 		!closedWeek &&
 		dayKeys[0] <= todayKey() &&
 		dayKeys.every((dk) => {
-			if (dk > todayKey()) return true;           // future day — skip
+			if (dk > todayKey()) return true;
-			if (!daysWithEntries.has(dk)) return true;  // no entries — skip
+			if (!daysWithEntries.has(dk)) return true;
-			return !!closedDaysMap[dk];                 // has entries → must be closed
+			return !!closedDaysMap[dk];
 		})
 	);
 
-	function prevWeek() { weekKey = offsetWeek(weekKey, -1); }
+	// Capabilities for the selected day, reactive on closedDaysMap updates.
-	function nextWeek() { weekKey = offsetWeek(weekKey, 1); }
-
-	// Today in this week?
-	const todayInWeek = $derived(dayKeys.includes(todayKey()));
-	const detailDayKey = $derived(todayInWeek ? todayKey() : null);
 	const detailCaps = $derived(
-		detailDayKey
+		dayCapabilities(selectedDay, todayKey(), !!closedDaysMap[selectedDay])
-			? dayCapabilities(detailDayKey, todayKey(), !!closedDaysMap[detailDayKey])
-			: null
 	);
-	function offsetWeek(wk: string, offset: number): string {
+
-		const [y, w] = wk.split('-W').map(Number);
+	// Scroll selected chip into view when selection changes.
-		const date = new Date(y, 0, 4);
+	let chipRefs: Record<string, HTMLElement> = {};
-		date.setDate(date.getDate() + (w - 1) * 7 + offset * 7);
+	$effect(() => {
-		const thu = new Date(date);
+		const el = chipRefs[selectedDay];
-		thu.setDate(date.getDate() + 4 - (date.getDay() || 7));
+		el?.scrollIntoView({ inline: 'nearest', block: 'nearest', behavior: 'smooth' });
-		const ys = new Date(thu.getFullYear(), 0, 1);
+	});
-		const weekNum = Math.ceil(((thu.getTime() - ys.getTime()) / 86400000 + 1) / 7);
-		return `${thu.getFullYear()}-W${String(weekNum).padStart(2, '0')}`;
-	}
 </script>
 
 <div class="week-view">
 	<div class="header">
-		<button onclick={prevWeek}>‹</button>
+		<button onclick={() => navigateWeek(-1)} aria-label="Previous week">‹</button>
 		<h1>Week {weekKey}</h1>
-		<button onclick={nextWeek}>›</button>
+		<button onclick={() => navigateWeek(1)} aria-label="Next week">›</button>
 	</div>
 
 	{#if error}<p class="error">{error}</p>{/if}
 
 	<!-- Day strip -->
-	<div class="day-strip" role="tablist" aria-label="Days of the week">
+	<!-- svelte-ignore a11y_interactive_supports_focus -->
+	<div
+		class="day-strip"
+		role="tablist"
+		aria-label="Days of the week"
+		onkeydown={handleStripKeydown}
+	>
 		{#each dayKeys as dk, i (dk)}
+			<span bind:this={chipRefs[dk]}>
 				<DayChip
 					dayKey={dk}
 					weekdayLabel={DAY_NAMES[i]}
@@ -145,9 +211,11 @@
 					kind={closedDaysMap[dk]?.kind ?? null}
 					closed={!!closedDaysMap[dk]}
 					isToday={dk === todayKey()}
-				selected={false}
+					selected={dk === selectedDay}
 					isWorkday={currentSettings ? isWorkday(dk, currentSettings.workdays_mask) : i < 5}
+					onclick={() => selectDay(dk)}
 				/>
+			</span>
 		{/each}
 	</div>
 
@@ -175,12 +243,11 @@
 		<button class="btn close-week" onclick={handleCloseWeek}>Close week</button>
 	{/if}
 
-	{#if detailDayKey && detailCaps}
+	<!-- Day detail panel -->
-		<div class="day-detail-panel">
+	<div class="day-detail-panel" role="tabpanel">
-			<h2 class="detail-heading">{detailDayKey}</h2>
+		<h2 class="detail-heading">{selectedDay}</h2>
-			<DayDetail dayKey={detailDayKey} capabilities={detailCaps} oninvalidate={load} />
+		<DayDetail dayKey={selectedDay} capabilities={detailCaps} oninvalidate={load} />
 	</div>
-	{/if}
 </div>
 
 <style>
@@ -196,7 +263,7 @@
 		overflow-x: auto;
 		scroll-snap-type: x mandatory;
 		-webkit-overflow-scrolling: touch;
-		padding-bottom: 0.25rem; /* room for scrollbar */
+		padding-bottom: 0.25rem;
 	}
 
 	.summary { background: #fff; border: 1px solid #dee2e6; border-radius: 8px; padding: 1rem; margin-bottom: 1rem; }