testing: move adapter e2e and automation to llama-server (llama.cpp) #1751

Summary

Our adapter serving and testing story is split across Ollama and llama.cpp, and the
ground is moving under the Ollama half: adapter creation is gone and the runtime path
is deprecated (#1633 has the decision on what we do there). llama-server already
serves Granite Switch adapter functions (PR #1736), and it's the layer Ollama itself
sits on.

This issue tracks focusing adapter testing and automation on llama-server.

Scope

• Adapter e2e and nightly coverage against llama-server, alongside the LocalHF path.
• Migrate what the Ollama removal blocked: test/scripts/build_ollama_uncertainty_adapter.sh
  and the uncertainty_ollama.py example need a llama.cpp-based provisioning route.
  Two cautions carry over from the Ollama removed LoRA-adapter GGUF *creation* (v0.34.1+) — breaks adapter provisioning for #1634, serving unaffected #1651 thread: merging is not equivalent for an
  aLoRA, and a served adapter should be checked for actually activating rather than
  assumed (bug(adapters): detect when an aLoRA cannot activate, and stop selecting it silently #1678 has the detection approach).
• A CI fixture strategy for llama-server-based adapter tests: models, adapter GGUFs,
  pins.

Notes

• Deliberately less urgent than the current consolidation work; nothing blocks on it.
• Different axis from Retarget adapter-resolution e2e tests off the temporary private repo to a public fixture #1655: that one retargets resolution e2e off a private HF fixture
  repo, this one is about the serving backend for adapter e2e.
• If design(adapters): freeze Ollama adapter support and redirect to llama.cpp, or maintain #1633 goes to freeze, this becomes the main home for adapter automation.

Related

• design(adapters): freeze Ollama adapter support and redirect to llama.cpp, or maintain #1633: the Ollama freeze-or-maintain decision.
• PR feat(backends): serve Granite Switch adapter functions on llama-server #1736: Granite Switch adapter functions on llama-server.
• Retarget adapter-resolution e2e tests off the temporary private repo to a public fixture #1655: adapter-resolution e2e retarget (different axis).