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/CommandLinkManager.tsx

@@ -1,14 +1,15 @@
 /**
  * CommandLinkManager — mounts as a child of <Article> and intercepts
  * clicks on :cmd[] directive spans to dispatch them via the shared
- * command dispatcher.
+ * command dispatcher. Errors are surfaced through the shared
+ * dispatchError signal, shown by JournalInput above the textarea.
  */
 
 import { Component, onCleanup } from "solid-js";
 import { useArticleDom } from "./Article";
 import { useJournalStream } from "./stores/journalStream";
 import { useJournalCompletions } from "./journal/completions";
-import { dispatchCommand } from "./journal/command-dispatcher";
+import { dispatchCommand, setDispatchError } from "./journal/command-dispatcher";
 
 export const CommandLinkManager: Component = () => {
   const contentDom = useArticleDom();
@@ -26,7 +27,7 @@ export const CommandLinkManager: Component = () => {
     e.stopPropagation();
     e.stopImmediatePropagation();
 
-    void dispatchCommand({
+    dispatchCommand({
       role: stream.myRole as "gm" | "player" | "observer",
       myName: stream.myName,
       command,
@@ -34,6 +35,10 @@ export const CommandLinkManager: Component = () => {
       statValues: stream.stats,
       statDefs: comp.data.stats,
       statTemplates: comp.data.statTemplates,
+    }).then((result) => {
+      if (!result.ok) {
+        setDispatchError(result.error);
+      }
     });
   };