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>

src/channels/whatsapp.test.ts

@@ -320,6 +320,9 @@ describe('WhatsAppChannel', () => {
       expect(opts.onChatMetadata).toHaveBeenCalledWith(
         'registered@g.us',
         expect.any(String),
+        undefined,
+        'whatsapp',
+        true,
       );
       expect(opts.onMessage).toHaveBeenCalledWith(
         'registered@g.us',
@@ -355,6 +358,9 @@ describe('WhatsAppChannel', () => {
       expect(opts.onChatMetadata).toHaveBeenCalledWith(
         'unregistered@g.us',
         expect.any(String),
+        undefined,
+        'whatsapp',
+        true,
       );
       expect(opts.onMessage).not.toHaveBeenCalled();
     });
@@ -579,6 +585,9 @@ describe('WhatsAppChannel', () => {
       expect(opts.onChatMetadata).toHaveBeenCalledWith(
         '1234567890@s.whatsapp.net',
         expect.any(String),
+        undefined,
+        'whatsapp',
+        false,
       );
     });
 
@@ -605,6 +614,9 @@ describe('WhatsAppChannel', () => {
       expect(opts.onChatMetadata).toHaveBeenCalledWith(
         'registered@g.us',
         expect.any(String),
+        undefined,
+        'whatsapp',
+        true,
       );
     });
 
@@ -631,6 +643,9 @@ describe('WhatsAppChannel', () => {
       expect(opts.onChatMetadata).toHaveBeenCalledWith(
         '0000000000@lid',
         expect.any(String),
+        undefined,
+        'whatsapp',
+        false,
       );
     });
   });