refactor(cli): centralize content registry building

Extract buildRegistryFromIndex and normalizePathKey from the CLI serve
command and the browser completions module into the shared
content-registry module. This ensures both paths produce identical
pathIndex/docContent, including the spark-injection pass that was
previously only applied in the CLI.

src/cli/content-registry.ts

@@ -63,6 +63,16 @@ export const EMPTY_REGISTRY: ContentRegistry = {
   docContent: {},
 };
 
+/**
+ * Normalize a file path into a stable registry key: forward slashes and a
+ * single leading `/`. Both the CLI filesystem walk and the browser folder
+ * scan funnel through this so identical files always share a key.
+ */
+export function normalizePathKey(path: string): string {
+  const normalized = path.split("\\").join("/");
+  return normalized.startsWith("/") ? normalized : `/${normalized}`;
+}
+
 // ---------------------------------------------------------------------------
 // Id / hash derivation (single source of truth)
 // ---------------------------------------------------------------------------
@@ -185,6 +195,46 @@ export function scanDoc(content: string, docPath: string): DocScanResult {
   return { stripped: rewritten, content: contentStore };
 }
 
+/**
+ * Build a `ContentRegistry` from a raw `{ path: content }` index.
+ *
+ * Shared by the CLI (`buildRegistry` in `commands/serve.ts`) and the browser
+ * folder scan (`scanClientSide` in `components/journal/completions.ts`) so
+ * both modes produce identical `pathIndex`/`docContent` — including the
+ * `data-spark` injection pass that only the CLI used to run.
+ *
+ * Keys are normalized via `normalizePathKey`; `.md` files are run through
+ * `scanDoc` and the spark-injection pass, other extensions are stored raw.
+ */
+export function buildRegistryFromIndex(
+  index: Record<string, string>,
+): ContentRegistry {
+  const registry: ContentRegistry = { pathIndex: {}, docContent: {} };
+
+  for (const [rawPath, content] of Object.entries(index)) {
+    const path = normalizePathKey(rawPath);
+    if (path.endsWith(".md")) {
+      const result = scanDoc(content, path);
+      registry.pathIndex[path] = result.stripped;
+      registry.docContent[path] = result.content;
+    } else {
+      registry.pathIndex[path] = content;
+    }
+  }
+
+  // Inject data-spark into real-file spark table directives (idempotent).
+  for (const [relPath, content] of Object.entries(registry.pathIndex)) {
+    if (!relPath.endsWith(".md")) continue;
+    registry.pathIndex[relPath] = injectSparkDirectives(
+      content,
+      relPath,
+      registry,
+    );
+  }
+
+  return registry;
+}
+
 // ---------------------------------------------------------------------------
 // Spark table coercion
 // ---------------------------------------------------------------------------