feat: add email outreach CLIs for backlink building

Add 4 new zero-dependency CLI tools for email outreach:
- hunter.js: Email finding/verification via Hunter.io (query param auth)
- snov.js: Email finding + drip campaigns via Snov.io (OAuth2 auth)
- lemlist.js: Cold email campaigns via Lemlist (Basic auth)
- instantly.js: Cold email at scale via Instantly.ai (query param auth)

Includes integration guides and registry/README updates.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tools/integrations/hunter.md

@@ -0,0 +1,90 @@
+# Hunter.io
+
+Email finding and verification platform for outreach and link building.
+
+## Capabilities
+
+| Integration | Available | Notes |
+|-------------|-----------|-------|
+| API | ✓ | REST API for domain search, email finder, verification |
+| MCP | - | Not available |
+| CLI | [✓](../clis/hunter.js) | Zero-dependency Node.js CLI |
+| SDK | - | API-only |
+
+## Authentication
+
+- **Type**: API Key (query parameter)
+- **Parameter**: `api_key={key}`
+- **Env var**: `HUNTER_API_KEY`
+- **Get key**: [Hunter dashboard > API](https://hunter.io/api-keys)
+
+## Common Agent Operations
+
+### Find emails for a domain
+
+```bash
+node tools/clis/hunter.js domain search --domain example.com --limit 10
+```
+
+### Find a specific person's email
+
+```bash
+node tools/clis/hunter.js email find --domain example.com --first-name John --last-name Doe
+```
+
+### Verify an email address
+
+```bash
+node tools/clis/hunter.js email verify --email john@example.com
+```
+
+### Count emails available for a domain
+
+```bash
+node tools/clis/hunter.js domain count --domain example.com
+```
+
+### Manage leads
+
+```bash
+# List leads
+node tools/clis/hunter.js leads list --limit 20
+
+# Create a lead
+node tools/clis/hunter.js leads create --email john@example.com --first-name John --last-name Doe --company "Example Inc"
+
+# Delete a lead
+node tools/clis/hunter.js leads delete --id 12345
+```
+
+### Manage campaigns
+
+```bash
+# List campaigns
+node tools/clis/hunter.js campaigns list
+
+# Get campaign details
+node tools/clis/hunter.js campaigns get --id 12345
+
+# Start/pause a campaign
+node tools/clis/hunter.js campaigns start --id 12345
+node tools/clis/hunter.js campaigns pause --id 12345
+```
+
+### Check account usage
+
+```bash
+node tools/clis/hunter.js account info
+```
+
+## Rate Limits
+
+- Free plan: 25 searches/month, 50 verifications/month
+- Paid plans scale with tier
+- API rate limit: 10 requests/second
+
+## Use Cases
+
+- **Link building**: Find email contacts at target domains for outreach
+- **Prospecting**: Build lead lists from company domains
+- **Verification**: Clean email lists before sending campaigns