[Core] Handle skipped warmup and encoder cache budget in extensible KV sizing
- With VLLM_ELASTIC_EP_SCALE_UP_LAUNCH, warmup (and hence the post-warmup
memory measurement) is skipped; commit the first-pass KV cache size
instead of failing on the empty per-worker measurement list.
- Reserve the encoder cache's full steady-state budget during V2 memory
profiling (mirroring the V1 runner): the runtime encoder cache can grow
to encoder_cache_size tokens of embeddings, far beyond the one batch of
dummy encoder outputs profiling held, so KV sizing over-committed for
multimodal models.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ho2gVXA5r7PhrM2sk8oJUn
Signed-off-by: Nick Hill <nickhill123@gmail.com>