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__/state.test.ts

@@ -0,0 +1,120 @@
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import fs from 'fs';
+import path from 'path';
+import {
+  readState,
+  writeState,
+  recordSkillApplication,
+  computeFileHash,
+  compareSemver,
+  recordCustomModification,
+  getCustomModifications,
+} from '../state.js';
+import {
+  createTempDir,
+  setupNanoclawDir,
+  createMinimalState,
+  writeState as writeStateHelper,
+  cleanup,
+} from './test-helpers.js';
+
+describe('state', () => {
+  let tmpDir: string;
+  const originalCwd = process.cwd();
+
+  beforeEach(() => {
+    tmpDir = createTempDir();
+    setupNanoclawDir(tmpDir);
+    process.chdir(tmpDir);
+  });
+
+  afterEach(() => {
+    process.chdir(originalCwd);
+    cleanup(tmpDir);
+  });
+
+  it('readState/writeState roundtrip', () => {
+    const state = {
+      skills_system_version: '0.1.0',
+      core_version: '1.0.0',
+      applied_skills: [],
+    };
+    writeState(state);
+    const result = readState();
+    expect(result.skills_system_version).toBe('0.1.0');
+    expect(result.core_version).toBe('1.0.0');
+    expect(result.applied_skills).toEqual([]);
+  });
+
+  it('readState throws when no state file exists', () => {
+    expect(() => readState()).toThrow();
+  });
+
+  it('readState throws when version is newer than current', () => {
+    writeStateHelper(tmpDir, {
+      skills_system_version: '99.0.0',
+      core_version: '1.0.0',
+      applied_skills: [],
+    });
+    expect(() => readState()).toThrow();
+  });
+
+  it('recordSkillApplication adds a skill', () => {
+    createMinimalState(tmpDir);
+    recordSkillApplication('my-skill', '1.0.0', { 'src/foo.ts': 'abc123' });
+    const state = readState();
+    expect(state.applied_skills).toHaveLength(1);
+    expect(state.applied_skills[0].name).toBe('my-skill');
+    expect(state.applied_skills[0].version).toBe('1.0.0');
+    expect(state.applied_skills[0].file_hashes).toEqual({ 'src/foo.ts': 'abc123' });
+  });
+
+  it('re-applying same skill replaces it', () => {
+    createMinimalState(tmpDir);
+    recordSkillApplication('my-skill', '1.0.0', { 'a.ts': 'hash1' });
+    recordSkillApplication('my-skill', '2.0.0', { 'a.ts': 'hash2' });
+    const state = readState();
+    expect(state.applied_skills).toHaveLength(1);
+    expect(state.applied_skills[0].version).toBe('2.0.0');
+    expect(state.applied_skills[0].file_hashes).toEqual({ 'a.ts': 'hash2' });
+  });
+
+  it('computeFileHash produces consistent sha256', () => {
+    const filePath = path.join(tmpDir, 'hashtest.txt');
+    fs.writeFileSync(filePath, 'hello world');
+    const hash1 = computeFileHash(filePath);
+    const hash2 = computeFileHash(filePath);
+    expect(hash1).toBe(hash2);
+    expect(hash1).toMatch(/^[a-f0-9]{64}$/);
+  });
+
+  describe('compareSemver', () => {
+    it('1.0.0 < 1.1.0', () => {
+      expect(compareSemver('1.0.0', '1.1.0')).toBeLessThan(0);
+    });
+
+    it('0.9.0 < 0.10.0', () => {
+      expect(compareSemver('0.9.0', '0.10.0')).toBeLessThan(0);
+    });
+
+    it('1.0.0 = 1.0.0', () => {
+      expect(compareSemver('1.0.0', '1.0.0')).toBe(0);
+    });
+  });
+
+  it('recordCustomModification adds to array', () => {
+    createMinimalState(tmpDir);
+    recordCustomModification('tweak', ['src/a.ts'], 'custom/001-tweak.patch');
+    const mods = getCustomModifications();
+    expect(mods).toHaveLength(1);
+    expect(mods[0].description).toBe('tweak');
+    expect(mods[0].files_modified).toEqual(['src/a.ts']);
+    expect(mods[0].patch_file).toBe('custom/001-tweak.patch');
+  });
+
+  it('getCustomModifications returns empty when none recorded', () => {
+    createMinimalState(tmpDir);
+    const mods = getCustomModifications();
+    expect(mods).toEqual([]);
+  });
+});