fix: prevent session creation loop when running without backend

Make getOrCreateSession idempotent by returning the existing active
session when called with no ID, instead of always creating a new one.
Use untrack() in the $effect to sever SvelteMap dependency so it only
re-runs on $page changes. Disable SSR on client-only routes, reduce
preload aggressiveness, and skip retries when already disconnected.

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

src/lib/services/orchestrator.ts

@@ -161,6 +161,11 @@ export async function* processRequest(
 	let lastError: OrchestratorError | null = null;
 
 	for (let attempt = 0; attempt <= MAX_RETRIES; attempt++) {
+		// Skip retries if already known disconnected
+		if (connectionStore.status === 'disconnected' && attempt > 0) {
+			break;
+		}
+
 		if (attempt > 0) {
 			connectionStore.setReconnecting();
 			const delay = backoffDelay(attempt - 1);