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/index.ts

@@ -0,0 +1,85 @@
+export { applySkill } from './apply.js';
+export { clearBackup, createBackup, restoreBackup } from './backup.js';
+export {
+  BACKUP_DIR,
+  BASE_DIR,
+  SKILLS_SCHEMA_VERSION,
+  CUSTOM_DIR,
+  LOCK_FILE,
+  NANOCLAW_DIR,
+  RESOLUTIONS_DIR,
+  SHIPPED_RESOLUTIONS_DIR,
+  STATE_FILE,
+} from './constants.js';
+export {
+  abortCustomize,
+  commitCustomize,
+  isCustomizeActive,
+  startCustomize,
+} from './customize.js';
+export { executeFileOps } from './file-ops.js';
+export { initNanoclawDir } from './init.js';
+export { acquireLock, isLocked, releaseLock } from './lock.js';
+export {
+  checkConflicts,
+  checkCoreVersion,
+  checkDependencies,
+  checkSystemVersion,
+  readManifest,
+} from './manifest.js';
+export {
+  cleanupMergeState,
+  isGitRepo,
+  mergeFile,
+  runRerere,
+  setupRerereAdapter,
+} from './merge.js';
+export {
+  loadPathRemap,
+  recordPathRemap,
+  resolvePathRemap,
+} from './path-remap.js';
+export { rebase } from './rebase.js';
+export { findSkillDir, replaySkills } from './replay.js';
+export type { ReplayOptions, ReplayResult } from './replay.js';
+export { uninstallSkill } from './uninstall.js';
+export { initSkillsSystem, migrateExisting } from './migrate.js';
+export {
+  clearAllResolutions,
+  findResolutionDir,
+  loadResolutions,
+  saveResolution,
+} from './resolution-cache.js';
+export { applyUpdate, previewUpdate } from './update.js';
+export {
+  compareSemver,
+  computeFileHash,
+  getAppliedSkills,
+  getCustomModifications,
+  readState,
+  recordCustomModification,
+  recordSkillApplication,
+  writeState,
+} from './state.js';
+export {
+  areRangesCompatible,
+  mergeDockerComposeServices,
+  mergeEnvAdditions,
+  mergeNpmDependencies,
+  runNpmInstall,
+} from './structured.js';
+export type {
+  AppliedSkill,
+  ApplyResult,
+  CustomModification,
+  FileOpsResult,
+  FileOperation,
+  MergeResult,
+  RebaseResult,
+  ResolutionMeta,
+  SkillManifest,
+  SkillState,
+  UninstallResult,
+  UpdatePreview,
+  UpdateResult,
+} from './types.js';