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__/file-ops.test.ts

@@ -0,0 +1,93 @@
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import fs from 'fs';
+import path from 'path';
+import { executeFileOps } from '../file-ops.js';
+import { createTempDir, cleanup } from './test-helpers.js';
+
+describe('file-ops', () => {
+  let tmpDir: string;
+  const originalCwd = process.cwd();
+
+  beforeEach(() => {
+    tmpDir = createTempDir();
+    process.chdir(tmpDir);
+  });
+
+  afterEach(() => {
+    process.chdir(originalCwd);
+    cleanup(tmpDir);
+  });
+
+  it('rename success', () => {
+    fs.writeFileSync(path.join(tmpDir, 'old.ts'), 'content');
+    const result = executeFileOps([
+      { type: 'rename', from: 'old.ts', to: 'new.ts' },
+    ], tmpDir);
+    expect(result.success).toBe(true);
+    expect(fs.existsSync(path.join(tmpDir, 'new.ts'))).toBe(true);
+    expect(fs.existsSync(path.join(tmpDir, 'old.ts'))).toBe(false);
+  });
+
+  it('move success', () => {
+    fs.writeFileSync(path.join(tmpDir, 'file.ts'), 'content');
+    const result = executeFileOps([
+      { type: 'move', from: 'file.ts', to: 'sub/file.ts' },
+    ], tmpDir);
+    expect(result.success).toBe(true);
+    expect(fs.existsSync(path.join(tmpDir, 'sub', 'file.ts'))).toBe(true);
+    expect(fs.existsSync(path.join(tmpDir, 'file.ts'))).toBe(false);
+  });
+
+  it('delete success', () => {
+    fs.writeFileSync(path.join(tmpDir, 'remove-me.ts'), 'content');
+    const result = executeFileOps([
+      { type: 'delete', path: 'remove-me.ts' },
+    ], tmpDir);
+    expect(result.success).toBe(true);
+    expect(fs.existsSync(path.join(tmpDir, 'remove-me.ts'))).toBe(false);
+  });
+
+  it('rename target exists produces error', () => {
+    fs.writeFileSync(path.join(tmpDir, 'a.ts'), 'a');
+    fs.writeFileSync(path.join(tmpDir, 'b.ts'), 'b');
+    const result = executeFileOps([
+      { type: 'rename', from: 'a.ts', to: 'b.ts' },
+    ], tmpDir);
+    expect(result.success).toBe(false);
+    expect(result.errors.length).toBeGreaterThan(0);
+  });
+
+  it('delete missing file produces warning not error', () => {
+    const result = executeFileOps([
+      { type: 'delete', path: 'nonexistent.ts' },
+    ], tmpDir);
+    expect(result.success).toBe(true);
+    expect(result.warnings.length).toBeGreaterThan(0);
+  });
+
+  it('move creates destination directory', () => {
+    fs.writeFileSync(path.join(tmpDir, 'src.ts'), 'content');
+    const result = executeFileOps([
+      { type: 'move', from: 'src.ts', to: 'deep/nested/dir/src.ts' },
+    ], tmpDir);
+    expect(result.success).toBe(true);
+    expect(fs.existsSync(path.join(tmpDir, 'deep', 'nested', 'dir', 'src.ts'))).toBe(true);
+  });
+
+  it('path escape produces error', () => {
+    fs.writeFileSync(path.join(tmpDir, 'file.ts'), 'content');
+    const result = executeFileOps([
+      { type: 'rename', from: 'file.ts', to: '../../escaped.ts' },
+    ], tmpDir);
+    expect(result.success).toBe(false);
+    expect(result.errors.length).toBeGreaterThan(0);
+  });
+
+  it('source missing produces error for rename', () => {
+    const result = executeFileOps([
+      { type: 'rename', from: 'missing.ts', to: 'new.ts' },
+    ], tmpDir);
+    expect(result.success).toBe(false);
+    expect(result.errors.length).toBeGreaterThan(0);
+  });
+});