Aggiunto connector Context7 (mcp_remote)

- URL: https://mcp.context7.com/mcp, trasporto streamable-http
- Auth: none (endpoint pubblico, free tier)
- Verify: MCP initialize probe (testato ✅)
- Icone SVG dal logo ufficiale Context7

Inoltre:
- Copiata docs/connector.manifest_guide.md da skald-circle/blueprint/
- Riferimento alla guida in SKALD.md

connectors/context7/verify.py

@@ -0,0 +1,66 @@
+#!/usr/bin/env python3
+"""Verify connectivity to Context7's hosted MCP server.
+
+Sends a lightweight JSON-RPC initialize to https://mcp.context7.com/mcp
+and checks for a successful response. No API key required — Context7's
+remote MCP endpoint works on the free tier without authentication.
+
+Prints a single JSON object on stdout:
+    {"ok": true,  "message": "Context7 MCP endpoint is reachable"}
+    {"ok": false, "message": "Context7 MCP endpoint is unreachable: <reason>"}
+
+Exit code is 0 on success, 1 on any failure.
+stdlib only (urllib).
+"""
+import json
+import sys
+import urllib.error
+import urllib.request
+
+
+def _result(ok, message):
+    print(json.dumps({"ok": ok, "message": message}))
+    sys.exit(0 if ok else 1)
+
+
+def main():
+    url = "https://mcp.context7.com/mcp"
+
+    body = json.dumps({
+        "jsonrpc": "2.0",
+        "id": 1,
+        "method": "initialize",
+        "params": {
+            "protocolVersion": "2025-03-26",
+            "capabilities": {},
+            "clientInfo": {"name": "skald-verify", "version": "1.0.0"},
+        },
+    }).encode("utf-8")
+
+    req = urllib.request.Request(
+        url,
+        data=body,
+        headers={
+            "Content-Type": "application/json",
+            "Accept": "application/json, text/event-stream",
+        },
+        method="POST",
+    )
+
+    try:
+        with urllib.request.urlopen(req, timeout=15) as resp:
+            data = resp.read().decode("utf-8")
+            if 200 <= resp.status < 300:
+                # Check for a valid JSON-RPC result in the SSE event stream
+                if '"result"' in data and '"serverInfo"' in data:
+                    _result(True, "Context7 MCP endpoint is reachable")
+                _result(False, f"Context7 returned unexpected response: {data[:200]}")
+            _result(False, f"Context7 returned HTTP {resp.status}")
+    except urllib.error.HTTPError as e:
+        _result(False, f"Context7 returned HTTP {e.code}: {e.reason}")
+    except Exception as e:
+        _result(False, f"Context7 MCP endpoint is unreachable: {e}")
+
+
+if __name__ == "__main__":
+    main()