fix(oneshot): --usage-file ledger reports auxiliary LLM spend

`hermes -z --usage-file` copied only the main-loop result, so title generation,
vision, compression, web_extract and background-review calls — recorded per task
in session_model_usage — never reached the pipeline ledger the flag advertises
as "so pipelines can always account for spend". The Insights page already folds
those rows in (#23270); the ledger is now consistent with it.

- SessionDB.auxiliary_usage_by_task(session_id): per-task sums over the
  session's compression lineage (aux calls bill to the id the turn started with
  while compression mints child ids mid-turn).
- oneshot snapshots aux usage before the turn and attaches the delta after it,
  so a resumed session's earlier runs are not re-billed.
- The report gains `auxiliary` (totals + `by_task`) and
  `total_including_auxiliary`; every existing key keeps its main-loop meaning.
- The auto-title upgrade runs on a daemon thread and can still be writing when
  the turn returns: title_generator tracks in-flight upgrade threads and
  oneshot joins them (bounded) before reading — no sleep, no eager read.

Fixes #112848. Direction shared with #112852 (@KoNit-K), which folded aux into
the headline counters; this keeps them backward compatible instead.

Co-authored-by: KoNit-K <124019182+KoNit-K@users.noreply.github.com>

agent/title_generator.py

@@ -9,6 +9,9 @@ import json
 import logging
 import os
 import re
+import threading
+import time
+import weakref
 from contextlib import suppress
 from typing import Any, Callable, Optional
 
@@ -19,6 +22,18 @@ from agent.message_content import flatten_message_text
 
 logger = logging.getLogger(__name__)
 
+# In-flight stage-2 upgrade threads. They bill their aux usage to the session from a daemon thread,
+# so a process that reads the ledger right before exit (``-z --usage-file``) must be able to join
+# them (bounded) instead of racing the write (#112848).
+_UPGRADE_THREADS: "weakref.WeakSet[threading.Thread]" = weakref.WeakSet()
+
+
+def wait_for_title_upgrades(timeout: float = 10.0) -> None:
+    """Bounded join of the auto-title threads still running; never raises."""
+    deadline = time.monotonic() + timeout
+    for thread in list(_UPGRADE_THREADS):
+        thread.join(max(0.0, deadline - time.monotonic()))
+
 # (task_name, exception) -> None; surfaces auxiliary failures so silent drops don't pile up as NULL titles.
 FailureCallback = Callable[[str, BaseException], None]
 # (title, source) -> None; source is the persisted provenance (``derived`` / ``llm``). Consumers paying a
@@ -528,9 +543,11 @@ def maybe_auto_title(
     # profile whose turn this is: a bare Thread starts with an empty context and lands on the launch
     # profile under multiplex, titling X's session with the default profile's model and billing its key.
     from agent.memory_provider import spawn_context_thread
-    spawn_context_thread(
+    upgrade = spawn_context_thread(
         auto_title_session, name="auto-title",
         args=(session_db, session_id, user_message),
         kwargs=dict(failure_callback=failure_callback, main_runtime=main_runtime, title_callback=title_callback,
                     runtime_validator=runtime_validator),
-    ).start()
+    )
+    _UPGRADE_THREADS.add(upgrade)
+    upgrade.start()