feat: add remix mode for spark table rolling

Introduces a `remix` option that allows each data column in a spark
table to be rolled independently. This is enabled via a `remix=true`
attribute in the directive's extra attributes.

Also refactors spark table scanning by moving markdown parsing logic
from the frontend to a new CLI-side `spark-scanner.ts` utility,
improving separation of concerns.

src/components/journal/JournalInput.tsx

@@ -128,7 +128,8 @@ export const JournalInput: Component = () => {
         const key = (parsed.payload as { key: string }).key;
         const match = comp.data.sparkTables.find((s) => s.slug === key);
         const csvPath = match?.csvPath ?? "";
-        const p = await resolveSparkPayload({ key, csvPath });
+        const remix = match?.remix ?? false;
+        const p = await resolveSparkPayload({ key, csvPath, remix });
         const result = sendMessage("spark", p);
         const r = unwrap(result);
         finish(r.ok, r.err);

src/components/journal/completions.ts

@@ -54,6 +54,7 @@ export interface SparkTableCompletion {
   filePath: string;
   csvPath: string;
   headers: string[];
+  remix: boolean;
 }
 
 export interface JournalCompletions {

src/components/journal/types/spark.tsx

@@ -70,10 +70,12 @@ export type SparkPayload = z.infer<typeof schema>;
  *
  * `key` is the combined slug (pageName-columnSlug).
  * `csvPath` is the resolved .csv file path from completions.
+ * `remix` controls whether each column gets an independent roll.
  */
 export async function resolveSparkPayload(raw: {
   key: string;
   csvPath: string;
+  remix: boolean;
 }): Promise<SparkPayload> {
   let csv: string;
   try {
@@ -89,7 +91,7 @@ export async function resolveSparkPayload(raw: {
     );
   }
 
-  const sparkResult = rollSparkTable(meta);
+  const sparkResult = rollSparkTable(meta, { remix: raw.remix });
   const firstRoll = rollFormula(meta.notation);
 
   return {