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__/path-remap.test.ts

@@ -0,0 +1,77 @@
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+
+import { loadPathRemap, recordPathRemap, resolvePathRemap } from '../path-remap.js';
+import {
+  cleanup,
+  createMinimalState,
+  createTempDir,
+  setupNanoclawDir,
+} from './test-helpers.js';
+
+describe('path-remap', () => {
+  let tmpDir: string;
+  const originalCwd = process.cwd();
+
+  beforeEach(() => {
+    tmpDir = createTempDir();
+    setupNanoclawDir(tmpDir);
+    createMinimalState(tmpDir);
+    process.chdir(tmpDir);
+  });
+
+  afterEach(() => {
+    process.chdir(originalCwd);
+    cleanup(tmpDir);
+  });
+
+  describe('resolvePathRemap', () => {
+    it('returns remapped path when entry exists', () => {
+      const remap = { 'src/old.ts': 'src/new.ts' };
+      expect(resolvePathRemap('src/old.ts', remap)).toBe('src/new.ts');
+    });
+
+    it('returns original path when no remap entry', () => {
+      const remap = { 'src/old.ts': 'src/new.ts' };
+      expect(resolvePathRemap('src/other.ts', remap)).toBe('src/other.ts');
+    });
+
+    it('returns original path when remap is empty', () => {
+      expect(resolvePathRemap('src/file.ts', {})).toBe('src/file.ts');
+    });
+  });
+
+  describe('loadPathRemap', () => {
+    it('returns empty object when no remap in state', () => {
+      const remap = loadPathRemap();
+      expect(remap).toEqual({});
+    });
+
+    it('returns remap from state', () => {
+      recordPathRemap({ 'src/a.ts': 'src/b.ts' });
+      const remap = loadPathRemap();
+      expect(remap).toEqual({ 'src/a.ts': 'src/b.ts' });
+    });
+  });
+
+  describe('recordPathRemap', () => {
+    it('records new remap entries', () => {
+      recordPathRemap({ 'src/old.ts': 'src/new.ts' });
+      expect(loadPathRemap()).toEqual({ 'src/old.ts': 'src/new.ts' });
+    });
+
+    it('merges with existing remap', () => {
+      recordPathRemap({ 'src/a.ts': 'src/b.ts' });
+      recordPathRemap({ 'src/c.ts': 'src/d.ts' });
+      expect(loadPathRemap()).toEqual({
+        'src/a.ts': 'src/b.ts',
+        'src/c.ts': 'src/d.ts',
+      });
+    });
+
+    it('overwrites existing key on conflict', () => {
+      recordPathRemap({ 'src/a.ts': 'src/b.ts' });
+      recordPathRemap({ 'src/a.ts': 'src/c.ts' });
+      expect(loadPathRemap()).toEqual({ 'src/a.ts': 'src/c.ts' });
+    });
+  });
+});