feat(frontend): add activate/deactivate toggle for tag rules

- Toggle button (filled/hollow circle) on each rule row
- Inactive rules dim to 45% opacity
- Toggle via delete + recreate with new is_active value
- Mock: track is_active per rule (Map instead of Set)
- Show all available tags by default in add-rule picker

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/components/tag/TagRuleEditor.svelte

@@ -57,6 +57,27 @@
 		}
 	}
 
+	async function toggleRule(rule: TagRule) {
+		if (busy) return;
+		busy = true;
+		error = '';
+		const thenTagId = rule.then_tag_id!;
+		const newActive = !rule.is_active;
+		try {
+			await api.delete(`/tags/${tagId}/rules/${thenTagId}`);
+			const updated = await api.post<TagRule>(`/tags/${tagId}/rules`, {
+				then_tag_id: thenTagId,
+				is_active: newActive,
+				apply_to_existing: false,
+			});
+			onRulesChange(rules.map((r) => r.then_tag_id === thenTagId ? updated : r));
+		} catch (e) {
+			error = e instanceof ApiError ? e.message : 'Failed to update rule';
+		} finally {
+			busy = false;
+		}
+	}
+
 	async function removeRule(thenTagId: string) {
 		if (busy) return;
 		busy = true;
@@ -86,12 +107,30 @@
 		<div class="rule-list">
 			{#each rules as rule (rule.then_tag_id)}
 				{@const t = tagForId(rule.then_tag_id)}
-				<div class="rule-row">
+				<div class="rule-row" class:inactive={!rule.is_active}>
 					{#if t}
 						<TagBadge tag={t} size="sm" />
 					{:else}
 						<span class="unknown">{rule.then_tag_name ?? rule.then_tag_id}</span>
 					{/if}
+					<button
+						class="toggle-btn"
+						class:active={rule.is_active}
+						onclick={() => toggleRule(rule)}
+						title={rule.is_active ? 'Deactivate rule' : 'Activate rule'}
+						aria-label={rule.is_active ? 'Deactivate rule' : 'Activate rule'}
+					>
+						{#if rule.is_active}
+							<svg width="12" height="12" viewBox="0 0 12 12" fill="none" aria-hidden="true">
+								<circle cx="6" cy="6" r="5" stroke="currentColor" stroke-width="1.5"/>
+								<circle cx="6" cy="6" r="2.5" fill="currentColor"/>
+							</svg>
+						{:else}
+							<svg width="12" height="12" viewBox="0 0 12 12" fill="none" aria-hidden="true">
+								<circle cx="6" cy="6" r="5" stroke="currentColor" stroke-width="1.5"/>
+							</svg>
+						{/if}
+					</button>
 					<button
 						class="remove-btn"
 						onclick={() => removeRule(rule.then_tag_id!)}
@@ -107,22 +146,29 @@
 	<!-- Add rule -->
 	<div class="add-section">
 		<div class="section-label">Add rule</div>
-		<input
-			class="search"
-			type="search"
-			placeholder="Search tags to add…"
-			bind:value={search}
-			autocomplete="off"
-		/>
-		{#if search.trim()}
-			<div class="tag-pick">
-				{#each filteredTags as t (t.id)}
-					<TagBadge tag={t} size="sm" onclick={() => addRule(t.id!)} />
-				{:else}
-					<span class="empty">No matching tags</span>
-				{/each}
-			</div>
-		{/if}
+		<div class="search-wrap">
+			<input
+				class="search"
+				type="search"
+				placeholder="Search tags to add…"
+				bind:value={search}
+				autocomplete="off"
+			/>
+			{#if search}
+				<button class="search-clear" onclick={() => (search = '')} aria-label="Clear search">
+					<svg width="14" height="14" viewBox="0 0 14 14" fill="none" aria-hidden="true">
+						<path d="M2 2l10 10M12 2L2 12" stroke="currentColor" stroke-width="1.8" stroke-linecap="round"/>
+					</svg>
+				</button>
+			{/if}
+		</div>
+		<div class="tag-pick">
+			{#each filteredTags as t (t.id)}
+				<TagBadge tag={t} size="sm" onclick={() => addRule(t.id!)} />
+			{:else}
+				<span class="empty">{search.trim() ? 'No matching tags' : 'All tags already added'}</span>
+			{/each}
+		</div>
 	</div>
 </div>
 
@@ -157,6 +203,31 @@
 		gap: 2px;
 	}
 
+	.rule-row.inactive {
+		opacity: 0.45;
+	}
+
+	.toggle-btn {
+		display: flex;
+		align-items: center;
+		justify-content: center;
+		background: none;
+		border: none;
+		color: var(--color-text-muted);
+		cursor: pointer;
+		padding: 2px 3px;
+		border-radius: 3px;
+		line-height: 1;
+	}
+
+	.toggle-btn.active {
+		color: var(--color-accent);
+	}
+
+	.toggle-btn:hover {
+		color: var(--color-text-primary);
+	}
+
 	.remove-btn {
 		background: none;
 		border: none;
@@ -193,6 +264,12 @@
 		gap: 6px;
 	}
 
+	.search-wrap {
+		position: relative;
+		display: flex;
+		align-items: center;
+	}
+
 	.search {
 		width: 100%;
 		box-sizing: border-box;
@@ -211,6 +288,27 @@
 		border-color: var(--color-accent);
 	}
 
+	.search-clear {
+		position: absolute;
+		right: 6px;
+		display: flex;
+		align-items: center;
+		justify-content: center;
+		width: 20px;
+		height: 20px;
+		border-radius: 50%;
+		border: none;
+		background: none;
+		color: var(--color-text-muted);
+		cursor: pointer;
+		padding: 0;
+	}
+
+	.search-clear:hover {
+		color: var(--color-text-primary);
+		background-color: color-mix(in srgb, var(--color-accent) 20%, transparent);
+	}
+
 	.tag-pick {
 		display: flex;
 		flex-wrap: wrap;