feat: add spark table completion and rolling support

Implement "spark tables" functionality, which allows users to roll
dice against markdown tables to retrieve specific values.

- Add `sparkTablesSource` to scan markdown files for tables starting
  with a dice notation (e.g., d6, d20).
- Implement `/spark` command in the journal to resolve and roll
  spark tables.
- Add a new message type `spark` with a dedicated UI component to
  render the results.
- Update completions API to include spark table metadata.

src/components/journal/JournalInput.tsx

@@ -24,6 +24,7 @@ import { sendMessage, useJournalStream } from "../stores/journalStream";
 import { linkPrefill, setLinkPrefill } from "../stores/reveal";
 import { useJournalCompletions, ensureCompletions } from "./completions";
 import { resolveRollPayload } from "./types/roll";
+import { resolveSparkPayload } from "./types/spark";
 
 // ---- Helpers ----
 
@@ -34,7 +35,7 @@ interface CompletionItem {
 }
 
 interface ParsedInput {
-  type: "chat" | "roll" | "link";
+  type: "chat" | "roll" | "spark" | "link";
   payload: Record<string, unknown>;
   error?: string;
 }
@@ -47,6 +48,13 @@ function parseInput(raw: string): ParsedInput {
     return { type: "roll", payload: { notation, label: notation } };
   }
 
+  if (raw.startsWith("/spark ")) {
+    const key = raw.slice("/spark ".length).trim();
+    if (!key)
+      return { type: "spark", payload: {}, error: "Spark table key required" };
+    return { type: "spark", payload: { key } };
+  }
+
   if (raw.startsWith("/link ")) {
     const arg = raw.slice("/link ".length).trim();
     if (!arg) return { type: "link", payload: {}, error: "Path required" };
@@ -57,8 +65,8 @@ function parseInput(raw: string): ParsedInput {
     return { type: "link", payload: { path, section } };
   }
 
-  // /roll or /link with no space — need to complete, don't send
-  if (raw === "/roll" || raw === "/link") {
+  // /roll, /spark, or /link with no space — need to complete, don't send
+  if (raw === "/roll" || raw === "/spark" || raw === "/link") {
     return { type: "chat", payload: {}, error: "Complete the command" };
   }
 
@@ -101,7 +109,7 @@ export const JournalInput: Component = () => {
 
   // ---- Send ----
 
-  function handleSend() {
+  async function handleSend() {
     const raw = text().trim();
     if (!raw) return;
 
@@ -142,6 +150,30 @@ export const JournalInput: Component = () => {
       return;
     }
 
+    // GM spark: resolve the spark table roll locally
+    if (parsed.type === "spark") {
+      try {
+        const key = (parsed.payload as { key: string }).key;
+        // Look up filePath from completions data
+        const match = comp.data.sparkTables.find((s) => s.slug === key);
+        const filePath = match?.filePath ?? "";
+        const p = await resolveSparkPayload({ key, filePath });
+        const result = sendMessage("spark", p);
+        if (!result.success) {
+          setError(result.error);
+        } else {
+          setText("");
+        }
+        setSending(false);
+        textareaRef?.focus();
+        return;
+      } catch (e) {
+        setError(e instanceof Error ? e.message : "Failed to roll spark table");
+        setSending(false);
+        return;
+      }
+    }
+
     const result = sendMessage(parsed.type, parsed.payload);
     if (!result.success) {
       setError(result.error);
@@ -172,6 +204,7 @@ export const JournalInput: Component = () => {
     const data = comp.data;
     const commands = [
       { label: "/roll", kind: "command" as const, insertText: "/roll " },
+      { label: "/spark", kind: "command" as const, insertText: "/spark " },
       { label: "/link", kind: "command" as const, insertText: "/link " },
     ];
 
@@ -206,6 +239,32 @@ export const JournalInput: Component = () => {
       }));
     }
 
+    // After /spark — show spark table suggestions
+    if (raw.startsWith("/spark ")) {
+      const prefix = raw.slice("/spark ".length).toLowerCase();
+      const matches = data.sparkTables
+        .filter(
+          (s) =>
+            s.slug.toLowerCase().includes(prefix) ||
+            s.label.toLowerCase().includes(prefix),
+        )
+        .slice(0, 8);
+      if (matches.length === 0) {
+        return [
+          {
+            label: "No spark tables found",
+            kind: "no-results",
+            insertText: "",
+          },
+        ];
+      }
+      return matches.map((s) => ({
+        label: `${s.filePath} § ${s.slug} (${s.notation})`,
+        kind: "value" as const,
+        insertText: `/spark ${s.slug}`,
+      }));
+    }
+
     // After /link — show article and heading suggestions
     if (raw.startsWith("/link ")) {
       const prefix = raw.slice("/link ".length).toLowerCase();