Skills engine v0.1 + multi-channel infrastructure (#307)

* refactor: multi-channel infrastructure with explicit channel/is_group tracking

- Add channels[] array and findChannel() routing in index.ts, replacing
  hardcoded whatsapp.* calls with channel-agnostic callbacks
- Add channel TEXT and is_group INTEGER columns to chats table with
  COALESCE upsert to protect existing values from null overwrites
- is_group defaults to 0 (safe: unknown chats excluded from groups)
- WhatsApp passes explicit channel='whatsapp' and isGroup to onChatMetadata
- getAvailableGroups filters on is_group instead of JID pattern matching
- findChannel logs warnings instead of silently dropping unroutable JIDs
- Migration backfills channel/is_group from JID patterns for existing DBs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* feat: skills engine v0.1 — deterministic skill packages with rerere resolution

Three-way merge engine for applying skill packages on top of a core
codebase. Skills declare which files they add/modify, and the engine
uses git merge-file for conflict detection with git rerere for
automatic resolution of previously-seen conflicts.

Key components:
- apply: three-way merge with backup/rollback safety net
- replay: clean-slate replay for uninstall and rebase
- update: core version updates with deletion detection
- rebase: bake applied skills into base (one-way)
- manifest: validation with path traversal protection
- resolution-cache: pre-computed rerere resolutions
- structured: npm deps, env vars, docker-compose merging
- CI: per-skill test matrix with conflict detection

151 unit tests covering merge, rerere, backup, replay, uninstall,
update, rebase, structured ops, and edge cases.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* feat: add Discord and Telegram skill packages

Skill packages for adding Discord and Telegram channels to NanoClaw.
Each package includes:
- Channel implementation (add/src/channels/)
- Three-way merge targets for index.ts, config.ts, routing.test.ts
- Intent docs explaining merge invariants
- Standalone integration tests
- manifest.yaml with dependency/conflict declarations

Applied via: npx tsx scripts/apply-skill.ts .claude/skills/add-discord
These are inert until applied — no runtime impact.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* remove unused docs (skills-system-status, implementation-guide)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

skills-engine/__tests__/test-helpers.ts

@@ -0,0 +1,99 @@
+import { execSync } from 'child_process';
+import fs from 'fs';
+import os from 'os';
+import path from 'path';
+import { stringify } from 'yaml';
+
+export function createTempDir(): string {
+  return fs.mkdtempSync(path.join(os.tmpdir(), 'nanoclaw-test-'));
+}
+
+export function setupNanoclawDir(tmpDir: string): void {
+  fs.mkdirSync(path.join(tmpDir, '.nanoclaw', 'base', 'src'), { recursive: true });
+  fs.mkdirSync(path.join(tmpDir, '.nanoclaw', 'backup'), { recursive: true });
+}
+
+export function writeState(tmpDir: string, state: any): void {
+  const statePath = path.join(tmpDir, '.nanoclaw', 'state.yaml');
+  fs.writeFileSync(statePath, stringify(state), 'utf-8');
+}
+
+export function createMinimalState(tmpDir: string): void {
+  writeState(tmpDir, {
+    skills_system_version: '0.1.0',
+    core_version: '1.0.0',
+    applied_skills: [],
+  });
+}
+
+export function createSkillPackage(tmpDir: string, opts: {
+  skill?: string;
+  version?: string;
+  core_version?: string;
+  adds?: string[];
+  modifies?: string[];
+  addFiles?: Record<string, string>;
+  modifyFiles?: Record<string, string>;
+  conflicts?: string[];
+  depends?: string[];
+  test?: string;
+  structured?: any;
+  file_ops?: any[];
+  post_apply?: string[];
+  min_skills_system_version?: string;
+  dirName?: string;
+}): string {
+  const skillDir = path.join(tmpDir, opts.dirName ?? 'skill-pkg');
+  fs.mkdirSync(skillDir, { recursive: true });
+
+  const manifest: Record<string, unknown> = {
+    skill: opts.skill ?? 'test-skill',
+    version: opts.version ?? '1.0.0',
+    description: 'Test skill',
+    core_version: opts.core_version ?? '1.0.0',
+    adds: opts.adds ?? [],
+    modifies: opts.modifies ?? [],
+    conflicts: opts.conflicts ?? [],
+    depends: opts.depends ?? [],
+    test: opts.test,
+    structured: opts.structured,
+    file_ops: opts.file_ops,
+  };
+  if (opts.post_apply) manifest.post_apply = opts.post_apply;
+  if (opts.min_skills_system_version) manifest.min_skills_system_version = opts.min_skills_system_version;
+
+  fs.writeFileSync(path.join(skillDir, 'manifest.yaml'), stringify(manifest));
+
+  if (opts.addFiles) {
+    const addDir = path.join(skillDir, 'add');
+    for (const [relPath, content] of Object.entries(opts.addFiles)) {
+      const fullPath = path.join(addDir, relPath);
+      fs.mkdirSync(path.dirname(fullPath), { recursive: true });
+      fs.writeFileSync(fullPath, content);
+    }
+  }
+
+  if (opts.modifyFiles) {
+    const modDir = path.join(skillDir, 'modify');
+    for (const [relPath, content] of Object.entries(opts.modifyFiles)) {
+      const fullPath = path.join(modDir, relPath);
+      fs.mkdirSync(path.dirname(fullPath), { recursive: true });
+      fs.writeFileSync(fullPath, content);
+    }
+  }
+
+  return skillDir;
+}
+
+export function initGitRepo(dir: string): void {
+  execSync('git init', { cwd: dir, stdio: 'pipe' });
+  execSync('git config user.email "test@test.com"', { cwd: dir, stdio: 'pipe' });
+  execSync('git config user.name "Test"', { cwd: dir, stdio: 'pipe' });
+  execSync('git config rerere.enabled true', { cwd: dir, stdio: 'pipe' });
+  fs.writeFileSync(path.join(dir, '.gitignore'), 'node_modules\n');
+  execSync('git add -A && git commit -m "init"', { cwd: dir, stdio: 'pipe' });
+}
+
+export function cleanup(dir: string): void {
+  fs.rmSync(dir, { recursive: true, force: true });
+}