refactor: merge /spark command into /roll

Consolidate the `/spark` command into `/roll` to simplify the CLI.
The `/roll` command now handles both dice notation and spark table
slugs.

- Update `parseInput` to treat `/roll` arguments as a generic string.
- Update `dispatchCommand` to check for spark table matches before
  evaluating dice notation or variable expressions.
- Update command completions to show both dice and spark table
  suggestions under `/roll`.
- Update documentation and UI placeholders to reflect the change.

src/components/journal/command-parser.ts

@@ -12,23 +12,17 @@ export interface CompletionItem {
 }
 
 export interface ParsedInput {
-  type: "chat" | "roll" | "spark" | "link" | "set" | "rolltag";
+  type: "chat" | "roll" | "link" | "set" | "rolltag";
   payload: Record<string, unknown>;
   error?: string;
 }
 
 export function parseInput(raw: string): ParsedInput {
   if (raw.startsWith("/roll ")) {
-    const notation = raw.slice("/roll ".length).trim();
-    if (!notation)
-      return { type: "roll", payload: {}, error: "需要骰子表达式" };
-    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: "需要种子表键名" };
-    return { type: "spark", payload: { key } };
+    const arg = raw.slice("/roll ".length).trim();
+    if (!arg)
+      return { type: "roll", payload: {}, error: "需要骰子表达式或种子表键名" };
+    return { type: "roll", payload: { arg } };
   }
 
   if (raw.startsWith("/link ")) {
@@ -69,7 +63,7 @@ export function parseInput(raw: string): ParsedInput {
     return { type: "set", payload: { key, expr } };
   }
 
-  if (raw === "/roll" || raw === "/spark" || raw === "/link" || raw === "/set") {
+  if (raw === "/roll" || raw === "/link" || raw === "/set") {
     return { type: "chat", payload: {}, error: "请补全命令" };
   }