docs: clarify CPU-only runtime path

[zcxGGmu]

Summary

• Clarify that the legacy local_chat / ktransformers.server examples in doc/en/install.md target CPU-GPU heterogeneous inference and require a CUDA-capable GPU.
• Point CPU-only users toward the newer KT-Kernel CPU backends, such as LLAMAFILE with GGUF weights.

Refs #337

Test Plan

• python documentation guard check for the new CPU-only runtime note
• git diff --check HEAD~1..HEAD

[greptile-apps]

Greptile Summary

This PR adds a single clarifying bullet to the "Preparation" section of doc/en/install.md, stating that local_chat and ktransformers.server require a CUDA-capable GPU and redirecting CPU-only users to the LLAMAFILE backend with a link to the llamafile operator guide.

• Adds a GPU-requirement note as the first bullet in the Preparation list, pointing CPU-only users to ./operators/llamafile.md (which exists in the repo).
• No code or configuration is changed; the diff is entirely documentation.

Confidence Score: 5/5

Documentation-only change with no impact on runtime behaviour; safe to merge.

The diff is five lines of Markdown inserted as a bullet point. The linked file (./operators/llamafile.md) is confirmed to exist in the repository, so the hyperlink is valid. No code, configuration, or build artefacts are touched.

Files Needing Attention: No files require special attention.

Important Files Changed

Filename	Overview
doc/en/install.md	Adds a 5-line note clarifying the CUDA GPU requirement for local_chat / ktransformers.server and linking CPU-only users to the llamafile operator guide. The referenced file exists and the link is well-formed.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[User reads install.md] --> B{Has a CUDA-capable GPU?}
    B -- Yes --> C[Follow CUDA setup steps]
    C --> D[local_chat / ktransformers.server\nCPU-GPU heterogeneous inference]
    B -- No --> E[CPU-only path]
    E --> F[Use KT-Kernel CPU backends\ne.g. LLAMAFILE with GGUF weights]
    F --> G[See llamafile operator guide]

Loading

_{Reviews (2): Last reviewed commit: "[docs]: clarify CPU-only install guidanc..." | Re-trigger Greptile}

[zcxGGmu]

Thanks for the review — I pushed b97970419bbb addressing the feedback.

Changes made:

• Softened the CPU-only runtime note and added a concrete link to the llamafile operator guide.

Validation:

• git diff --check — passed.
• Content guard — passed: CPU-only note links to llamafile docs and avoids unsupported legacy wording.
• Diff scan — passed: no secret/debug-marker patterns found.