fix(aibox): batch G audit fixes - llm hardening, thread lifecycle, cancel propagation, db transactions
P-series (llm_client): truncate non-transient HTTP error body to 200 chars, cap Retry-After at 3600s, validate fallback profiles (missing model skipped with warning), dedupe fallback list, remove dead _cancelled flag, document FailoverClient concurrency contract.
N-series (aibox/registry): batch-level drain thread with try/finally reclamation (N2), subagent cancel propagation via shared parent event + watcher thread (N5), /new reset moved off event loop (N3), streaming forward bounded by TOOL_MAX_RESULT_LENGTH (N8), persona path boundary check (N12), broadcast except narrowed + discard (N13), per-connection task set registration (N14).
db/history: FTS5 quote escaping (N7), mark_as_triggered single BEGIN IMMEDIATE transaction (N10), LIMIT parameterization (L1), archive filename collision suffix (N16).
Tests: +20 cases in test_g_fixes.py, full suite 375 passed.
qing
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