feat(slack): new Slack notification/ChatOps integration

Slack Web API, 8 commands: send message (text/Block Kit), list/create channel,
invite to channel, set topic, get user, add reaction. Bot-token auth, stdlib-only.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

integrations/slack/scripts/create_channel.py

@@ -0,0 +1,51 @@
+import json, os, sys, urllib.parse, urllib.request, urllib.error
+
+BASE = "https://slack.com/api"
+
+
+def _cfg():
+    return json.loads(os.environ.get("INTEGRATION_SECRETS", "{}"))
+
+
+def _inputs():
+    return json.loads(os.environ.get("INTEGRATION_INPUTS", "{}"))
+
+
+def call(method_name, cfg, body=None, params=None, http="POST"):
+    url = BASE + "/" + method_name
+    if params:
+        url += "?" + urllib.parse.urlencode({k: v for k, v in params.items() if v not in (None, "")})
+    data = json.dumps(body).encode("utf-8") if body is not None else None
+    headers = {"Authorization": "Bearer " + str(cfg.get("bot_token", "")), "Accept": "application/json"}
+    if data is not None:
+        headers["Content-Type"] = "application/json; charset=utf-8"
+    req = urllib.request.Request(url, data=data, headers=headers, method=http)
+    with urllib.request.urlopen(req, timeout=60) as r:
+        resp = json.loads(r.read() or "{}")
+    if not resp.get("ok"):
+        raise Exception("Slack error: " + str(resp.get("error") or resp))
+    return resp
+
+
+def _run(fn):
+    try:
+        print(json.dumps(fn(_cfg(), _inputs())))
+    except urllib.error.HTTPError as e:
+        print(json.dumps({"error": "HTTP " + str(e.code), "detail": e.read().decode("utf-8", "replace")}))
+        sys.exit(1)
+    except Exception as e:
+        print(json.dumps({"error": str(e)}))
+        sys.exit(1)
+
+
+def main(cfg, inputs):
+    name = str(inputs.get("name") or "").strip()
+    if not name:
+        raise Exception("name is required")
+
+    is_private = bool(inputs.get("is_private") or False)
+
+    return call("conversations.create", cfg, body={"name": name, "is_private": is_private})
+
+
+_run(main)