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/command-loader.ts

@@ -0,0 +1,53 @@
+import { existsSync, readdirSync, readFileSync } from "fs"
+import { basename, join } from "path"
+import { parseFrontmatter } from "../../shared/frontmatter"
+import { isMarkdownFile } from "../../shared/file-utils"
+import { sanitizeModelField } from "../../shared/model-sanitizer"
+import { log } from "../../shared/logger"
+import type { CommandDefinition, CommandFrontmatter } from "../claude-code-command-loader/types"
+import type { LoadedPlugin } from "./types"
+
+export function loadPluginCommands(plugins: LoadedPlugin[]): Record<string, CommandDefinition> {
+  const commands: Record<string, CommandDefinition> = {}
+
+  for (const plugin of plugins) {
+    if (!plugin.commandsDir || !existsSync(plugin.commandsDir)) continue
+
+    const entries = readdirSync(plugin.commandsDir, { withFileTypes: true })
+
+    for (const entry of entries) {
+      if (!isMarkdownFile(entry)) continue
+
+      const commandPath = join(plugin.commandsDir, entry.name)
+      const commandName = basename(entry.name, ".md")
+      const namespacedName = `${plugin.name}:${commandName}`
+
+      try {
+        const content = readFileSync(commandPath, "utf-8")
+        const { data, body } = parseFrontmatter<CommandFrontmatter>(content)
+
+        const wrappedTemplate = `<command-instruction>\n${body.trim()}\n</command-instruction>\n\n<user-request>\n$ARGUMENTS\n</user-request>`
+        const formattedDescription = `(plugin: ${plugin.name}) ${data.description || ""}`
+
+        const definition = {
+          name: namespacedName,
+          description: formattedDescription,
+          template: wrappedTemplate,
+          agent: data.agent,
+          model: sanitizeModelField(data.model, "claude-code"),
+          subtask: data.subtask,
+          argumentHint: data["argument-hint"],
+        }
+
+        const { name: _name, argumentHint: _argumentHint, ...openCodeCompatible } = definition
+        commands[namespacedName] = openCodeCompatible as CommandDefinition
+
+        log(`Loaded plugin command: ${namespacedName}`, { path: commandPath })
+      } catch (error) {
+        log(`Failed to load plugin command: ${commandPath}`, error)
+      }
+    }
+  }
+
+  return commands
+}