feat: implement shared dispatch error signal

Introduce a shared `dispatchError` signal in the command dispatcher
to unify error reporting across different components. This allows
`CommandLinkManager` to surface errors through the `JournalInput`
UI, ensuring that errors from `:cmd[]` directive clicks are visible
to the user.

src/components/journal/command-dispatcher.ts

@@ -6,6 +6,7 @@
  */
 
 import { sendMessage } from "../stores/journalStream";
+import { createSignal } from "solid-js";
 import { parseInput } from "./command-parser";
 import { resolveRollPayload } from "./types/roll";
 import { resolveSparkPayload } from "./types/spark";
@@ -26,6 +27,14 @@ export type DispatchResult =
   | { ok: true }
   | { ok: false; error: string };
 
+/**
+ * Shared signal for dispatch errors from any source (typed or cmd-link clicks).
+ * Components that show errors (JournalInput) read from here; callers that
+ * want errors surfaced (CommandLinkManager) write to it.
+ */
+export const [dispatchError, setDispatchError] =
+  createSignal<string | null>(null);
+
 // ---------------------------------------------------------------------------
 // Main dispatch
 // ---------------------------------------------------------------------------
@@ -60,25 +69,25 @@ export async function dispatchCommand(
   // Observers can only send chat
   if (ctx.role === "observer") {
     const result = sendMessage("chat", { text: raw });
-    return unwrap(result);
+    return finish(unwrap(result));
   }
 
   const prefixed = raw.startsWith("/") ? raw : "/" + raw;
   const parsed = parseInput(prefixed);
-  if (parsed.error) return { ok: false, error: parsed.error };
+  if (parsed.error) return finish({ ok: false, error: parsed.error });
 
   // Players: chat + stat commands only
   if (ctx.role === "player") {
     if (parsed.type === "chat") {
       const result = sendMessage("chat", { text: raw });
-      return unwrap(result);
+      return finish(unwrap(result));
     }
 
     if (parsed.type === "stat") {
-      return dispatchStat(parsed.payload as Record<string, unknown>, ctx);
+      return finish(dispatchStat(parsed.payload as Record<string, unknown>, ctx));
     }
 
-    return { ok: false, error: "玩家只能发送聊天消息或使用 /stat 命令" };
+    return finish({ ok: false, error: "玩家只能发送聊天消息或使用 /stat 命令" });
   }
 
   // GM: all commands
@@ -87,7 +96,7 @@ export async function dispatchCommand(
       parsed.payload as { notation: string; label?: string },
     );
     const result = sendMessage("roll", p);
-    return unwrap(result);
+    return finish(unwrap(result));
   }
 
   if (parsed.type === "spark") {
@@ -98,21 +107,27 @@ export async function dispatchCommand(
       const remix = match?.remix ?? false;
       const p = await resolveSparkPayload({ key, csvPath, remix });
       const result = sendMessage("spark", p);
-      return unwrap(result);
+      return finish(unwrap(result));
     } catch (e) {
-      return {
+      return finish({
         ok: false,
         error: e instanceof Error ? e.message : "种子表掷骰失败",
-      };
+      });
     }
   }
 
   if (parsed.type === "stat") {
-    return dispatchStat(parsed.payload as Record<string, unknown>, ctx);
+    return finish(dispatchStat(parsed.payload as Record<string, unknown>, ctx));
   }
 
   const result = sendMessage(parsed.type, parsed.payload);
-  return unwrap(result);
+  return finish(unwrap(result));
+}
+
+/** Update the shared error signal and return the result (pass-through). */
+function finish(r: DispatchResult): DispatchResult {
+  setDispatchError(r.ok ? null : r.error);
+  return r;
 }
 
 // ---------------------------------------------------------------------------