fix: generate skill/slashcommand descriptions synchronously when pre-provided (#1087)

* fix: generate skill/slashcommand tool descriptions synchronously when pre-provided

When skills are passed via options (pre-resolved), build the tool description
synchronously instead of fire-and-forget async. This eliminates the race
condition where the description getter returns the bare prefix before the
async cache-warming microtask completes.

Fixes #1039

* chore: changes by sisyphus-dev-ai

---------

Co-authored-by: sisyphus-dev-ai <sisyphus-dev-ai@users.noreply.github.com>

src/tools/slashcommand/tools.ts

@@ -210,8 +210,12 @@ export function createSlashcommandTool(options: SlashcommandToolOptions = {}): T
     return cachedDescription
   }
 
-  // Pre-warm the cache immediately
-  buildDescription()
+  if (options.commands !== undefined && options.skills !== undefined) {
+    const allItems = [...options.commands, ...options.skills.map(skillToCommandInfo)]
+    cachedDescription = buildDescriptionFromItems(allItems)
+  } else {
+    buildDescription()
+  }
 
   return tool({
     get description() {