feat: http_post tool, nc_talk_history tool, local orchestrator retry

- http_post: POST to external URLs with per-user URL prefix allowlist
  (home/{user}/http_allowlist.json); admin-only, confirm-required
- nc_talk_history: read recent NC Talk messages via Basic Auth (requires
  nc_username + nc_app_password in channels.json under nextcloud)
- openai_orchestrator: _chat_with_retry() wraps both API calls with
  exponential backoff (3 attempts, 1s/2s) on connection errors and
  transient status codes (429, 500, 502, 503, 504)
- Docs updated: CLAUDE.md, HELP.md, TODO, MASTER, ROADMAP (50 tools)

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

cortex/openai_orchestrator.py

@@ -21,7 +21,7 @@ import asyncio
 import json
 import logging
 
-from openai import AsyncOpenAI
+from openai import AsyncOpenAI, APIConnectionError, APIStatusError
 
 from config import settings
 from orchestrator_engine import OrchestrateCheckpoint, OrchestratorResult
@@ -286,7 +286,7 @@ async def _run_from_messages(
         if active_tools:
             call_kwargs["tools"] = active_tools
             call_kwargs["tool_choice"] = "auto"
-        response = await client.chat.completions.create(**call_kwargs)
+        response = await _chat_with_retry(client, **call_kwargs)
 
         choice = response.choices[0]
         msg = choice.message
@@ -345,7 +345,7 @@ async def _run_from_messages(
                 conf_call: dict = {"model": model_name, "messages": messages, "tool_choice": "none"}
                 if active_tools:
                     conf_call["tools"] = active_tools
-                conf_resp = await client.chat.completions.create(**conf_call)
+                conf_resp = await _chat_with_retry(client, **conf_call)
                 final_response = conf_resp.choices[0].message.content or (
                     "This action requires your explicit confirmation before it can proceed."
                 )
@@ -386,6 +386,30 @@ async def _run_from_messages(
     return final_response, None
 
 
+_RETRY_STATUSES = {429, 500, 502, 503, 504}
+_MAX_API_RETRIES = 3
+
+
+async def _chat_with_retry(client, **kwargs):
+    """Wrap chat.completions.create with exponential backoff on transient errors."""
+    last_exc: Exception = RuntimeError("No attempts made")
+    for attempt in range(_MAX_API_RETRIES):
+        try:
+            return await client.chat.completions.create(**kwargs)
+        except APIConnectionError as e:
+            last_exc = e
+            logger.warning("OpenAI connection error (attempt %d/%d): %s", attempt + 1, _MAX_API_RETRIES, e)
+        except APIStatusError as e:
+            if e.status_code in _RETRY_STATUSES:
+                last_exc = e
+                logger.warning("OpenAI status %d (attempt %d/%d): %s", e.status_code, attempt + 1, _MAX_API_RETRIES, e)
+            else:
+                raise
+        if attempt < _MAX_API_RETRIES - 1:
+            await asyncio.sleep(2 ** attempt)  # 1s, 2s
+    raise last_exc
+
+
 def _build_client(
     model_cfg: dict | None,
     user_role: str = "user",