Embeddings bypassed the front request queue (relayed unqueued) and the
per-model lease scheduler, so the only guard was ratelimit.py's per-IP fixed
window. A single authenticated client could pipeline unlimited embedding
requests straight at the GPU — which on the Polaris/RX580 Vulkan backend wedged
the SDMA ring (ring timeout -> GPU reset -> device lost from bus).

Add _embed_admission() around create_embeddings: bounded concurrency, backlog
shedding (429 when in-flight >= concurrency + backlog), and optional pacing
between GPU starts. Tunable via CODERAI_EMBED_MAX_CONCURRENCY (2),
CODERAI_EMBED_MAX_BACKLOG (32), CODERAI_EMBED_MIN_INTERVAL_MS (0). Bump 0.1.79.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0196Gm4PNkcuybDj9yfcz3CR