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/agent-loader.ts

@@ -0,0 +1,69 @@
+import { existsSync, readdirSync, readFileSync } from "fs"
+import { basename, join } from "path"
+import type { AgentConfig } from "@opencode-ai/sdk"
+import { parseFrontmatter } from "../../shared/frontmatter"
+import { isMarkdownFile } from "../../shared/file-utils"
+import { log } from "../../shared/logger"
+import type { AgentFrontmatter } from "../claude-code-agent-loader/types"
+import type { LoadedPlugin } from "./types"
+
+function parseToolsConfig(toolsStr?: string): Record<string, boolean> | undefined {
+  if (!toolsStr) return undefined
+
+  const tools = toolsStr
+    .split(",")
+    .map((tool) => tool.trim())
+    .filter(Boolean)
+
+  if (tools.length === 0) return undefined
+
+  const result: Record<string, boolean> = {}
+  for (const tool of tools) {
+    result[tool.toLowerCase()] = true
+  }
+  return result
+}
+
+export function loadPluginAgents(plugins: LoadedPlugin[]): Record<string, AgentConfig> {
+  const agents: Record<string, AgentConfig> = {}
+
+  for (const plugin of plugins) {
+    if (!plugin.agentsDir || !existsSync(plugin.agentsDir)) continue
+
+    const entries = readdirSync(plugin.agentsDir, { withFileTypes: true })
+
+    for (const entry of entries) {
+      if (!isMarkdownFile(entry)) continue
+
+      const agentPath = join(plugin.agentsDir, entry.name)
+      const agentName = basename(entry.name, ".md")
+      const namespacedName = `${plugin.name}:${agentName}`
+
+      try {
+        const content = readFileSync(agentPath, "utf-8")
+        const { data, body } = parseFrontmatter<AgentFrontmatter>(content)
+
+        const originalDescription = data.description || ""
+        const formattedDescription = `(plugin: ${plugin.name}) ${originalDescription}`
+
+        const config: AgentConfig = {
+          description: formattedDescription,
+          mode: "subagent",
+          prompt: body.trim(),
+        }
+
+        const toolsConfig = parseToolsConfig(data.tools)
+        if (toolsConfig) {
+          config.tools = toolsConfig
+        }
+
+        agents[namespacedName] = config
+        log(`Loaded plugin agent: ${namespacedName}`, { path: agentPath })
+      } catch (error) {
+        log(`Failed to load plugin agent: ${agentPath}`, error)
+      }
+    }
+  }
+
+  return agents
+}