feat(agent): add skip_background_review flag to AIAgent constructor

Phase 8 of the Hermes Agent token leak mitigation plan
(ralplan-hermes-token-leaks.md §3.9). Adds a boolean kwarg
`skip_background_review` (default False) to AIAgent.__init__ that
suppresses the end-of-turn _spawn_background_review fork.

Each background review fork instantiates a new AIAgent with its own
~15K input tokens + up to 8 LLM iterations, accumulating ~30K tokens
per event in the worst case. On cron sessions there is no
human-in-the-loop benefit from the review (no skill-creation pressure,
nobody curating MEMORY.md), so the cost is pure waste.

The end-of-turn guard now reads:

    if (final_response and not interrupted
            and not getattr(self, "skip_background_review", False)
            and (_should_review_memory or _should_review_skills)):

skip_memory=True already disables the memory-review trigger; this
flag is the explicit single-switch off for both review paths.

Defaults to False, so behavior is unchanged for gateway/CLI callers
that omit the kwarg.

Tests: 5 new unit tests in tests/agent/test_skip_background_review.py
covering the default value, flag persistence, the gate short-circuit,
the gate fall-through, and a source-text assertion that the cron
scheduler sets the flag to True (separate commit).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

agent/turn_finalizer.py

@@ -721,7 +721,15 @@ def finalize_turn(
 
     # Background memory/skill review — runs AFTER the response is delivered
     # so it never competes with the user's task for model attention.
-    if final_response and not interrupted and (_should_review_memory or _should_review_skills):
+    # Suppressed when skip_background_review=True (e.g. cron) — review forks
+    # spawn another AIAgent (~30K tokens / event) and cron sessions have no
+    # human-in-the-loop benefit from the review.
+    if (
+        final_response
+        and not interrupted
+        and not getattr(agent, "skip_background_review", False)
+        and (_should_review_memory or _should_review_skills)
+    ):
         try:
             agent._spawn_background_review(
                 messages_snapshot=list(messages),