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>

gateway/status.py

@@ -83,8 +83,7 @@ def _looks_like_gateway_process(pid: int) -> bool:
     """Return True when the live PID still looks like the Hermes gateway."""
     cmdline = _read_process_cmdline(pid)
     if not cmdline:
-        # If we cannot inspect the process, fall back to the liveness check.
-        return True
+        return False
 
     patterns = (
         "hermes_cli.main gateway",
@@ -94,6 +93,24 @@ def _looks_like_gateway_process(pid: int) -> bool:
     return any(pattern in cmdline for pattern in patterns)
 
 
+def _record_looks_like_gateway(record: dict[str, Any]) -> bool:
+    """Validate gateway identity from PID-file metadata when cmdline is unavailable."""
+    if record.get("kind") != _GATEWAY_KIND:
+        return False
+
+    argv = record.get("argv")
+    if not isinstance(argv, list) or not argv:
+        return False
+
+    cmdline = " ".join(str(part) for part in argv)
+    patterns = (
+        "hermes_cli.main gateway",
+        "hermes gateway",
+        "gateway/run.py",
+    )
+    return any(pattern in cmdline for pattern in patterns)
+
+
 def _build_pid_record() -> dict:
     return {
         "pid": os.getpid(),
@@ -325,8 +342,9 @@ def get_running_pid() -> Optional[int]:
         return None
 
     if not _looks_like_gateway_process(pid):
-        remove_pid_file()
-        return None
+        if not _record_looks_like_gateway(record):
+            remove_pid_file()
+            return None
 
     return pid