feat(genomic): add SkillInstaller for fast skill installation via shallow clone

packages/genomic/src/index.ts

@@ -20,6 +20,8 @@ export * from './git/git-cloner';
 export * from './git/types';
 export * from './scaffolder/template-scaffolder';
 export * from './scaffolder/types';
+export * from './skills/skill-installer';
+export * from './skills/types';
 export * from './template/templatizer';
 export * from './template/types';
 export * from './utils/npm-version-check';

packages/genomic/src/skills/skill-installer.ts

@@ -0,0 +1,126 @@
+import * as fs from 'fs';
+import * as path from 'path';
+
+import { CacheManager } from '../cache/cache-manager';
+import { GitCloner } from '../git/git-cloner';
+import { BoilerplateSkill } from '../scaffolder/types';
+import { SkillInstallOptions, SkillInstallResult } from './types';
+
+const DEFAULT_TTL_MS = 7 * 24 * 60 * 60 * 1000; // 7 days
+const SKILLS_DIR = path.join('.agents', 'skills');
+
+/**
+ * Installs skills from git repositories using shallow clones.
+ *
+ * Much faster than `npx skills add` because it:
+ * - Clones with `--depth 1` (shallow)
+ * - Caches source repos (subsequent installs are instant)
+ * - Copies skill directories directly (no npm download)
+ *
+ * @example
+ * ```typescript
+ * const installer = new SkillInstaller({ toolName: 'pgpm' });
+ * const result = installer.install(
+ *   [{ source: 'constructive-io/constructive', skills: ['pgpm'] }],
+ *   '/path/to/workspace'
+ * );
+ * ```
+ */
+export class SkillInstaller {
+  private gitCloner: GitCloner;
+  private cacheManager: CacheManager;
+
+  constructor(options?: SkillInstallOptions) {
+    this.gitCloner = new GitCloner();
+    this.cacheManager = new CacheManager({
+      toolName: options?.toolName ?? 'genomic',
+      ttl: options?.cacheTtlMs ?? DEFAULT_TTL_MS,
+      baseDir: options?.cacheBaseDir,
+    });
+  }
+
+  /**
+   * Install skills from their source repositories into a target directory.
+   *
+   * For each skill entry, clones the source repo (shallow, cached) and
+   * copies `.agents/skills/<name>/` into `<targetDir>/.agents/skills/<name>/`.
+   *
+   * Non-fatal: failures are collected and returned, never thrown.
+   */
+  install(skills: BoilerplateSkill[], targetDir: string): SkillInstallResult {
+    const installed: string[] = [];
+    const failed: SkillInstallResult['failed'] = [];
+
+    // Group skills by source to avoid cloning the same repo multiple times
+    const bySource = new Map<string, string[]>();
+    for (const entry of skills) {
+      const existing = bySource.get(entry.source) ?? [];
+      existing.push(...entry.skills);
+      bySource.set(entry.source, existing);
+    }
+
+    for (const [source, skillNames] of bySource) {
+      let repoDir: string;
+      try {
+        repoDir = this.ensureRepo(source);
+      } catch (err) {
+        const msg = err instanceof Error ? err.message : String(err);
+        for (const skill of skillNames) {
+          failed.push({ skill, source, error: msg });
+        }
+        continue;
+      }
+
+      for (const skillName of skillNames) {
+        const sourcePath = path.join(repoDir, SKILLS_DIR, skillName);
+
+        if (!fs.existsSync(sourcePath)) {
+          failed.push({
+            skill: skillName,
+            source,
+            error: `Skill not found in source: ${SKILLS_DIR}/${skillName}`,
+          });
+          continue;
+        }
+
+        try {
+          const destPath = path.join(targetDir, SKILLS_DIR, skillName);
+          fs.mkdirSync(path.dirname(destPath), { recursive: true });
+          fs.cpSync(sourcePath, destPath, { recursive: true });
+          installed.push(skillName);
+        } catch (err) {
+          const msg = err instanceof Error ? err.message : String(err);
+          failed.push({ skill: skillName, source, error: msg });
+        }
+      }
+    }
+
+    return { installed, failed };
+  }
+
+  /**
+   * Clone (or retrieve from cache) a skill source repository.
+   */
+  private ensureRepo(source: string): string {
+    const url = this.gitCloner.normalizeUrl(source);
+    const cacheKey = this.cacheManager.createKey(url);
+
+    const expiredMetadata = this.cacheManager.checkExpiration(cacheKey);
+    if (expiredMetadata) {
+      this.cacheManager.clear(cacheKey);
+    }
+
+    const cached = this.cacheManager.get(cacheKey);
+    if (cached && !expiredMetadata) {
+      return cached;
+    }
+
+    const dest = path.join(this.cacheManager.getReposDir(), cacheKey);
+    this.gitCloner.clone(url, dest, {
+      depth: 1,
+      singleBranch: true,
+    });
+    this.cacheManager.set(cacheKey, dest);
+    return dest;
+  }
+}

packages/genomic/src/skills/types.ts

@@ -0,0 +1,37 @@
+export interface SkillInstallOptions {
+  /**
+   * Tool name for cache directory naming (e.g., 'pgpm' -> ~/.pgpm/cache).
+   * Sharing the same toolName as your TemplateScaffolder means skills
+   * and templates share the same cache directory.
+   * @default 'genomic'
+   */
+  toolName?: string;
+
+  /**
+   * Cache TTL in milliseconds for cloned skill source repos.
+   * @default 7 days
+   */
+  cacheTtlMs?: number;
+
+  /**
+   * Base directory for cache storage.
+   * Useful for tests to avoid touching the real home directory.
+   */
+  cacheBaseDir?: string;
+}
+
+export interface SkillInstallResult {
+  /** Successfully installed skill names */
+  installed: string[];
+  /** Skills that failed to install */
+  failed: SkillInstallFailure[];
+}
+
+export interface SkillInstallFailure {
+  /** Skill name that failed */
+  skill: string;
+  /** Source repository */
+  source: string;
+  /** Error description */
+  error: string;
+}