refactor(claude-code-plugin-loader): split loader.ts into per-type loaders

Extract plugin component loading into dedicated modules:
- discovery.ts: plugin directory detection
- plugin-path-resolver.ts: path resolution logic
- agent-loader.ts, command-loader.ts, hook-loader.ts
- mcp-server-loader.ts, skill-loader.ts

src/features/claude-code-plugin-loader/skill-loader.ts

@@ -0,0 +1,60 @@
+import { existsSync, readdirSync, readFileSync } from "fs"
+import { join } from "path"
+import { parseFrontmatter } from "../../shared/frontmatter"
+import { resolveSymlink } from "../../shared/file-utils"
+import { sanitizeModelField } from "../../shared/model-sanitizer"
+import { log } from "../../shared/logger"
+import type { CommandDefinition } from "../claude-code-command-loader/types"
+import type { SkillMetadata } from "../opencode-skill-loader/types"
+import type { LoadedPlugin } from "./types"
+
+export function loadPluginSkillsAsCommands(
+  plugins: LoadedPlugin[],
+): Record<string, CommandDefinition> {
+  const skills: Record<string, CommandDefinition> = {}
+
+  for (const plugin of plugins) {
+    if (!plugin.skillsDir || !existsSync(plugin.skillsDir)) continue
+
+    const entries = readdirSync(plugin.skillsDir, { withFileTypes: true })
+
+    for (const entry of entries) {
+      if (entry.name.startsWith(".")) continue
+
+      const skillPath = join(plugin.skillsDir, entry.name)
+      if (!entry.isDirectory() && !entry.isSymbolicLink()) continue
+
+      const resolvedPath = resolveSymlink(skillPath)
+      const skillMdPath = join(resolvedPath, "SKILL.md")
+      if (!existsSync(skillMdPath)) continue
+
+      try {
+        const content = readFileSync(skillMdPath, "utf-8")
+        const { data, body } = parseFrontmatter<SkillMetadata>(content)
+
+        const skillName = data.name || entry.name
+        const namespacedName = `${plugin.name}:${skillName}`
+        const originalDescription = data.description || ""
+        const formattedDescription = `(plugin: ${plugin.name} - Skill) ${originalDescription}`
+
+        const wrappedTemplate = `<skill-instruction>\nBase directory for this skill: ${resolvedPath}/\nFile references (@path) in this skill are relative to this directory.\n\n${body.trim()}\n</skill-instruction>\n\n<user-request>\n$ARGUMENTS\n</user-request>`
+
+        const definition = {
+          name: namespacedName,
+          description: formattedDescription,
+          template: wrappedTemplate,
+          model: sanitizeModelField(data.model),
+        }
+
+        const { name: _name, ...openCodeCompatible } = definition
+        skills[namespacedName] = openCodeCompatible as CommandDefinition
+
+        log(`Loaded plugin skill: ${namespacedName}`, { path: resolvedPath })
+      } catch (error) {
+        log(`Failed to load plugin skill: ${skillPath}`, error)
+      }
+    }
+  }
+
+  return skills
+}