fix(frank-large): load the model as its native 3-way split, not a concatenated file

The first cutover crash-looped the unit with 'invalid split file name':
the fetch script concatenated the three split parts into a single GGUF,
but part 1's header carries ggml.file_count=3, so the byte-correct
concatenation still advertises itself as a split and the loader demands
a -NNNNN-of-NNNNN filename.

- serve-frank-large.sh: -m points at part 1; llama.cpp loads the split
  natively (parts 2-3 auto-discovered in the same directory)
- deploy-remote.sh: LLM_LARGE_MODEL gate path follows
- download-frank-large-unsloth.sh: assembly removed; the parts ARE the
  canonical payload, verified against live Hub LFS oids
- docs: runbook model section + troubleshooting note, AGENTS.md, log
- the redundant 87 GiB assembled file is staged on dankclaw at
  ~/.AGENTTRASH/20260921-frank-large-assembled/

scripts/deploy-remote.sh

@@ -1084,7 +1084,7 @@ deploy_anubis() {
 # STRIX-Orca), which had replaced the halogen-flash-server quadlet. The
 # port gate is the same as every cutover since 2026-09-16: nothing starts
 # until 7770 is released.
-LLM_LARGE_MODEL="${LLM_LARGE_MODEL:-/home/dank/models/Qwen3.8-Flash-Next-UD-IQ4_XS/Qwen3.8-Flash-Next-UD-IQ4_XS.gguf}"
+LLM_LARGE_MODEL="${LLM_LARGE_MODEL:-/home/dank/models/Qwen3.8-Flash-Next-UD-IQ4_XS/UD-IQ4_XS/Qwen3.8-Flash-Next-UD-IQ4_XS-00001-of-00003.gguf}"
 LLM_LARGE_DRAFT="${LLM_LARGE_DRAFT:-/home/dank/models/Qwen3.8-Flash-Next-UD-IQ4_XS/mtp/mtp-Qwen3.8-Flash-Next-shared-Q8_0.gguf}"
 
 retire_halogen_large_quadlet() {