Add /add-deltachat skill

Skill files only — copied from PR #2192 (channels branch).
Source adapter (src/channels/deltachat.ts) lives on the channels
branch and is installed by the skill.

Co-Authored-By: Axel McLaren <scm@axml.uk>
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.claude/skills/add-deltachat/VERIFY.md

@@ -0,0 +1,54 @@
+# Verify DeltaChat
+
+## 1. Check the adapter started
+
+```bash
+grep "Channel adapter started.*deltachat" logs/nanoclaw.log | tail -1
+```
+
+Expected: `Channel adapter started { channel: 'deltachat', type: 'deltachat' }`
+
+## 2. Check IMAP/SMTP connectivity
+
+Replace with your provider's hostnames from `.env`:
+
+```bash
+DC_IMAP=$(grep '^DC_IMAP_HOST=' .env | cut -d= -f2)
+DC_SMTP=$(grep '^DC_SMTP_HOST=' .env | cut -d= -f2)
+
+bash -c "echo >/dev/tcp/$DC_IMAP/993" && echo "IMAP open" || echo "IMAP blocked"
+bash -c "echo >/dev/tcp/$DC_SMTP/587" && echo "SMTP open" || echo "SMTP blocked"
+```
+
+## 3. End-to-end message test
+
+1. Open DeltaChat on your device
+2. Add the bot email address as a contact
+3. Send a message
+4. The bot should respond within a few seconds
+
+If nothing arrives, check:
+
+```bash
+grep "DeltaChat" logs/nanoclaw.log | tail -20
+grep "DeltaChat" logs/nanoclaw.error.log | tail -10
+```
+
+## 4. Check messaging group was created
+
+```bash
+sqlite3 data/v2.db \
+  "SELECT id, platform_id, name FROM messaging_groups WHERE channel_type='deltachat' ORDER BY created_at DESC LIMIT 5"
+```
+
+If a row appears, the inbound routing is working. If not, the adapter isn't receiving the message — check logs for `DeltaChat: error handling incoming message`.
+
+## 5. Verify user access
+
+If the message arrived but the agent didn't respond, the sender may not have access:
+
+```bash
+sqlite3 data/v2.db "SELECT id, display_name FROM users WHERE id LIKE 'deltachat:%'"
+```
+
+Grant access as shown in the SKILL.md "Grant user access" section.