fix(honcho): isolate session routing for multi-user gateway (#1500)

Salvaged from PR #1470 by adavyas.

Core fix: Honcho tool calls in a multi-session gateway could route to
the wrong session because honcho_tools.py relied on process-global
state. Now threads session context through the call chain:
  AIAgent._invoke_tool() → handle_function_call() → registry.dispatch()
  → handler **kw → _resolve_session_context()

Changes:
- Add _resolve_session_context() to prefer per-call context over globals
- Plumb honcho_manager + honcho_session_key through handle_function_call
- Add sync_honcho=False to run_conversation() for synthetic flush turns
- Pass honcho_session_key through gateway memory flush lifecycle
- Harden gateway PID detection when /proc cmdline is unreadable
- Make interrupt test scripts import-safe for pytest-xdist
- Wrap BibTeX examples in Jekyll raw blocks for docs build
- Fix thread-order-dependent assertion in client lifecycle test
- Expand Honcho docs: session isolation, lifecycle, routing internals

Dropped from original PR:
- Indentation change in _create_request_openai_client that would move
  client creation inside the lock (causes unnecessary contention)

Co-authored-by: adavyas <adavyas@users.noreply.github.com>

model_tools.py

@@ -267,6 +267,8 @@ def handle_function_call(
     task_id: Optional[str] = None,
     user_task: Optional[str] = None,
     enabled_tools: Optional[List[str]] = None,
+    honcho_manager: Optional[Any] = None,
+    honcho_session_key: Optional[str] = None,
 ) -> str:
     """
     Main function call dispatcher that routes calls to the tool registry.
@@ -306,12 +308,16 @@ def handle_function_call(
                 function_name, function_args,
                 task_id=task_id,
                 enabled_tools=sandbox_enabled,
+                honcho_manager=honcho_manager,
+                honcho_session_key=honcho_session_key,
             )
 
         return registry.dispatch(
             function_name, function_args,
             task_id=task_id,
             user_task=user_task,
+            honcho_manager=honcho_manager,
+            honcho_session_key=honcho_session_key,
         )
 
     except Exception as e: