refactor: add mcp and skills to llmService

- Deleted the llmSkillsService implementation and its associated methods
for listing provider skills.
- Updated tests to use llmService instead of llmMcpService and
llmSkillsService for handling MCP and skills functionalities.
- Adjusted test cases to reflect the new service structure while
maintaining existing functionality.

server/src/modules/llm/providers/runtimes/codex-skills.runtime.ts

@@ -0,0 +1,47 @@
+import os from 'node:os';
+import path from 'node:path';
+
+import type { IProviderSkillsRuntime, ProviderSkill, ProviderSkillScope } from '@/modules/llm/providers/provider.interface.js';
+import {
+  deduplicateDirectories,
+  deduplicateSkills,
+  findGitRepoRoot,
+  listSkillsFromDirectory,
+} from '@/modules/llm/providers/runtimes/skills-runtime.utils.js';
+
+/**
+ * Codex skills runtime backed by repo/user/admin/system skill directories.
+ */
+export class CodexSkillsRuntime implements IProviderSkillsRuntime {
+  /**
+   * Lists all available Codex skills from documented directories.
+   */
+  async listSkills(options?: { workspacePath?: string }): Promise<ProviderSkill[]> {
+    const workspacePath = path.resolve(options?.workspacePath ?? process.cwd());
+    const home = os.homedir();
+    const repoRoot = await findGitRepoRoot(workspacePath);
+    const candidateDirectories: Array<{ scope: ProviderSkillScope; directory: string }> = [
+      { scope: 'repo', directory: path.join(workspacePath, '.agents', 'skills') },
+      { scope: 'repo', directory: path.join(workspacePath, '..', '.agents', 'skills') },
+      { scope: 'user', directory: path.join(home, '.agents', 'skills') },
+      { scope: 'admin', directory: path.join(path.sep, 'etc', 'codex', 'skills') },
+      { scope: 'system', directory: path.join(home, '.codex', 'skills', '.system') },
+    ];
+    if (repoRoot) {
+      candidateDirectories.push({ scope: 'repo', directory: path.join(repoRoot, '.agents', 'skills') });
+    }
+
+    const skills: ProviderSkill[] = [];
+    for (const candidate of deduplicateDirectories(candidateDirectories)) {
+      const loadedSkills = await listSkillsFromDirectory({
+        provider: 'codex',
+        scope: candidate.scope,
+        skillsDirectory: candidate.directory,
+        invocationPrefix: '$',
+      });
+      skills.push(...loadedSkills);
+    }
+
+    return deduplicateSkills(skills);
+  }
+}