Add faithful single-choice chat results, tool stream activity, error-frame retries, and isolated protocol caching.
Reject empty cached completions with the same value predicate as transport, add regression coverage, and adopt Apache-2.0.
HEDGE__STALL_AFTER_S triggers a cross-source hedge when the primary
leg stalls mid-stream (independent of HEDGE__AFTER_S); two-phase
hedge window with event recheck discipline; watchdog-killed primary
converges on the surviving hedge leg. STREAM__STALL_THRESHOLD_MS
(1000ms default) adjustable via env/settings/constructor. Assembly
guards: ValueError on never-opening windows, embedding/OCR scope
warning (B4). Batch D 14 tests red-to-green, 1688 unit+contracts.
iomgaa