fix(skill): support YAML array format for allowed-tools field (#1163)

Fixes #1021

The allowed-tools field in skill frontmatter now supports both formats:
- Space-separated string: 'allowed-tools: Read Write Edit Bash'
- YAML array: 'allowed-tools: [Read, Write, Edit, Bash]'
- Multi-line YAML array format also works

Previously, skills using YAML array format would silently fail to parse,
causing them to not appear in the <available_skills> list.

Changes:
- Updated parseAllowedTools() in loader.ts, async-loader.ts, and merger.ts
  to handle both string and string[] types
- Updated SkillMetadata type to accept string | string[] for allowed-tools
- Added 4 test cases covering all allowed-tools formats

src/features/opencode-skill-loader/merger.ts

@@ -9,6 +9,14 @@ import { parseFrontmatter } from "../../shared/frontmatter"
 import { sanitizeModelField } from "../../shared/model-sanitizer"
 import { deepMerge } from "../../shared/deep-merge"
 
+function parseAllowedToolsFromMetadata(allowedTools: string | string[] | undefined): string[] | undefined {
+  if (!allowedTools) return undefined
+  if (Array.isArray(allowedTools)) {
+    return allowedTools.map(t => t.trim()).filter(Boolean)
+  }
+  return allowedTools.split(/\s+/).filter(Boolean)
+}
+
 const SCOPE_PRIORITY: Record<SkillScope, number> = {
   builtin: 1,
   config: 2,
@@ -119,7 +127,7 @@ $ARGUMENTS
   }
 
   const allowedTools = entry["allowed-tools"] ||
-    (fileMetadata["allowed-tools"] ? fileMetadata["allowed-tools"].split(/\s+/).filter(Boolean) : undefined)
+    (fileMetadata["allowed-tools"] ? parseAllowedToolsFromMetadata(fileMetadata["allowed-tools"]) : undefined)
 
   return {
     name,