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/migrate.ts

@@ -0,0 +1,74 @@
+import { execFileSync } from 'child_process';
+import fs from 'fs';
+import path from 'path';
+
+import { BASE_DIR, CUSTOM_DIR, NANOCLAW_DIR } from './constants.js';
+import { initNanoclawDir } from './init.js';
+import { recordCustomModification } from './state.js';
+
+export function initSkillsSystem(): void {
+  initNanoclawDir();
+  console.log('Skills system initialized. .nanoclaw/ directory created.');
+}
+
+export function migrateExisting(): void {
+  const projectRoot = process.cwd();
+
+  // First, do a fresh init
+  initNanoclawDir();
+
+  // Then, diff current files against base to capture modifications
+  const baseSrcDir = path.join(projectRoot, BASE_DIR, 'src');
+  const srcDir = path.join(projectRoot, 'src');
+  const customDir = path.join(projectRoot, CUSTOM_DIR);
+  const patchRelPath = path.join(CUSTOM_DIR, 'migration.patch');
+
+  try {
+    let diff: string;
+    try {
+      diff = execFileSync('diff', ['-ruN', baseSrcDir, srcDir], {
+        encoding: 'utf-8',
+        maxBuffer: 10 * 1024 * 1024,
+      });
+    } catch (err: unknown) {
+      // diff exits 1 when files differ — that's expected
+      const execErr = err as { status?: number; stdout?: string };
+      if (execErr.status === 1 && execErr.stdout) {
+        diff = execErr.stdout;
+      } else {
+        throw err;
+      }
+    }
+
+    if (diff.trim()) {
+      fs.mkdirSync(customDir, { recursive: true });
+      fs.writeFileSync(
+        path.join(projectRoot, patchRelPath),
+        diff,
+        'utf-8',
+      );
+
+      // Extract modified file paths from the diff
+      const filesModified = [...diff.matchAll(/^diff -ruN .+ (.+)$/gm)]
+        .map((m) => path.relative(projectRoot, m[1]))
+        .filter((f) => !f.startsWith('.nanoclaw'));
+
+      // Record in state so the patch is visible to the tracking system
+      recordCustomModification(
+        'Pre-skills migration',
+        filesModified,
+        patchRelPath,
+      );
+
+      console.log(
+        'Custom modifications captured in .nanoclaw/custom/migration.patch',
+      );
+    } else {
+      console.log('No custom modifications detected.');
+    }
+  } catch {
+    console.log('Could not generate diff. Continuing with clean base.');
+  }
+
+  console.log('Migration complete. Skills system ready.');
+}