refactor: code review improvements — fix bugs, extract shared utilities, add README

- Fix reactivity bug: use SvelteMap instead of Map in sessions store
- Fix theme listener memory leak: guard against double-init, return cleanup function
- Fix transport singleton ignoring different endpoints
- Fix form/button type mismatch in MessageInput
- Add safer retry validation in chat page
- Extract shared utilities: date formatting, session config check, result source config
- Extract shared components: Backdrop, PageHeader
- Extract orchestration composable from chat page (310→85 lines of script)
- Consolidate AuditTimeline switch functions into config record
- Move sample data to dedicated module
- Add dark mode support for LineageTree SVG colors
- Memoize leaf count computation in LineageTree
- Update README with usage guide and project structure

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

src/lib/components/FinalResult.svelte

@@ -1,6 +1,7 @@
 <script lang="ts">
 	import type { SubagentResult } from '$lib/proto/llm_multiverse/v1/common_pb';
-	import { ResultStatus, ResultQuality, ResultSource } from '$lib/proto/llm_multiverse/v1/common_pb';
+	import { ResultStatus, ResultQuality } from '$lib/proto/llm_multiverse/v1/common_pb';
+	import { resultSourceConfig } from '$lib/types/resultSource';
 
 	let { result }: { result: SubagentResult } = $props();
 
@@ -26,14 +27,7 @@
 		}
 	});
 
-	const sourceLabel = $derived.by(() => {
-		switch (result.source) {
-			case ResultSource.TOOL_OUTPUT: return 'Tool Output';
-			case ResultSource.MODEL_KNOWLEDGE: return 'Model Knowledge';
-			case ResultSource.WEB: return 'Web';
-			default: return '';
-		}
-	});
+	const sourceBadge = $derived(resultSourceConfig(result.source));
 </script>
 
 <div class="mx-4 mb-3 rounded-xl border {statusConfig.border} {statusConfig.bg} p-4">
@@ -46,9 +40,9 @@
 				{qualityLabel}
 			</span>
 		{/if}
-		{#if sourceLabel}
-			<span class="rounded-full bg-purple-100 dark:bg-purple-900/40 px-2.5 py-0.5 text-xs font-medium text-purple-800 dark:text-purple-300">
-				{sourceLabel}
+		{#if sourceBadge.label !== 'Unspecified'}
+			<span class="rounded-full {sourceBadge.bg} px-2.5 py-0.5 text-xs font-medium {sourceBadge.text}">
+				{sourceBadge.label}
 			</span>
 		{/if}
 	</div>