unify single user and multi user behaviour

site/src/lib/dataloader.ts

@@ -161,10 +161,16 @@ export async function loadActivity(
 /**
  * Load athlete profile. Athlete data is not stored locally yet, so this is
  * always a network fetch with a graceful null on failure.
+ *
+ * @param baseUrl    Site base URL (used to build the default path)
+ * @param athleteUrl Explicit full URL — use for per-user pages in multi-user mode
  */
-export async function loadAthlete(baseUrl: string): Promise<Record<string, unknown> | null> {
+export async function loadAthlete(
+  baseUrl: string,
+  athleteUrl?: string,
+): Promise<Record<string, unknown> | null> {
   try {
-    return await fetchJSON(`${baseUrl}data/athlete.json`);
+    return await fetchJSON(athleteUrl ?? `${baseUrl}data/athlete.json`);
   } catch {
     return null;
   }

site/src/lib/manifest.ts

@@ -0,0 +1,37 @@
+/**
+ * Build-time helpers for reading the BAS shard manifest.
+ * Only import this in .astro frontmatter — it uses Node.js APIs.
+ */
+import { readFileSync } from 'node:fs';
+import { join, resolve } from 'node:path';
+
+export function findDataDir(): string | null {
+  const candidates = [
+    process.env.BINCIO_DATA_DIR,
+    resolve(process.cwd(), 'public', 'data'),
+    resolve(process.cwd(), '..', 'bincio_data'),
+  ].filter(Boolean) as string[];
+  return candidates.find(d => {
+    try { readFileSync(join(d, 'index.json')); return true; } catch { return false; }
+  }) ?? null;
+}
+
+export interface ShardHandle {
+  handle: string;
+  /** Shard URL as written in the manifest (relative to data root). */
+  url: string;
+}
+
+export function readShardHandles(): ShardHandle[] {
+  try {
+    const dataDir = findDataDir();
+    if (!dataDir) return [];
+    const root = JSON.parse(readFileSync(join(dataDir, 'index.json'), 'utf-8'));
+    const shards: Array<{ handle?: string; url: string }> = root.shards ?? [];
+    return shards
+      .filter(s => !!s.handle)
+      .map(s => ({ handle: s.handle!, url: s.url }));
+  } catch {
+    return [];
+  }
+}