feat(skill-loader): add skill loader that converts skills to commands

Skills are loaded from:
- ~/.claude/skills/ (user scope)
- .claude/skills/ (project scope)

Each skill directory contains SKILL.md with frontmatter metadata.

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

src/features/skill-loader/index.ts

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+export * from "./types"
+export * from "./loader"

src/features/skill-loader/loader.ts

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+import { existsSync, readdirSync, readFileSync, statSync, readlinkSync } from "fs"
+import { homedir } from "os"
+import { join, resolve } from "path"
+import { parseFrontmatter } from "../../shared/frontmatter"
+import { sanitizeModelField } from "../../shared/model-sanitizer"
+import type { CommandDefinition } from "../command-loader/types"
+import type { SkillScope, SkillMetadata, LoadedSkillAsCommand } from "./types"
+
+function loadSkillsFromDir(skillsDir: string, scope: SkillScope): LoadedSkillAsCommand[] {
+  if (!existsSync(skillsDir)) {
+    return []
+  }
+
+  const entries = readdirSync(skillsDir, { withFileTypes: true })
+  const skills: LoadedSkillAsCommand[] = []
+
+  for (const entry of entries) {
+    if (entry.name.startsWith(".")) continue
+
+    const skillPath = join(skillsDir, entry.name)
+
+    if (!entry.isDirectory() && !entry.isSymbolicLink()) continue
+
+    let resolvedPath = skillPath
+    if (statSync(skillPath, { throwIfNoEntry: false })?.isSymbolicLink()) {
+      resolvedPath = resolve(skillPath, "..", readlinkSync(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 originalDescription = data.description || ""
+      const formattedDescription = `(${scope} - Skill) ${originalDescription}`
+
+      const wrappedTemplate = `<skill-instruction>
+${body.trim()}
+</skill-instruction>
+
+<user-request>
+$ARGUMENTS
+</user-request>`
+
+      const definition: CommandDefinition = {
+        name: skillName,
+        description: formattedDescription,
+        template: wrappedTemplate,
+        model: sanitizeModelField(data.model),
+      }
+
+      skills.push({
+        name: skillName,
+        path: resolvedPath,
+        definition,
+        scope,
+      })
+    } catch {
+      continue
+    }
+  }
+
+  return skills
+}
+
+export function loadUserSkillsAsCommands(): Record<string, CommandDefinition> {
+  const userSkillsDir = join(homedir(), ".claude", "skills")
+  const skills = loadSkillsFromDir(userSkillsDir, "user")
+  return skills.reduce((acc, skill) => {
+    acc[skill.name] = skill.definition
+    return acc
+  }, {} as Record<string, CommandDefinition>)
+}
+
+export function loadProjectSkillsAsCommands(): Record<string, CommandDefinition> {
+  const projectSkillsDir = join(process.cwd(), ".claude", "skills")
+  const skills = loadSkillsFromDir(projectSkillsDir, "project")
+  return skills.reduce((acc, skill) => {
+    acc[skill.name] = skill.definition
+    return acc
+  }, {} as Record<string, CommandDefinition>)
+}

src/features/skill-loader/types.ts

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+import type { CommandDefinition } from "../command-loader/types"
+
+export type SkillScope = "user" | "project"
+
+export interface SkillMetadata {
+  name: string
+  description: string
+  model?: string
+}
+
+export interface LoadedSkillAsCommand {
+  name: string
+  path: string
+  definition: CommandDefinition
+  scope: SkillScope
+}