docs(radiance): reference the engine's options, plugins and conversion

Nine pages under LLM/ document the upstream radiance engine at 8da043c:
- engine shape, plugin model, RAD2 container, ABI and environment
- every serve flag grouped with defaults and the law behind each knob
- the HTTP surface, request fields and refusal classes
- rad-convert, the recipe language, quantisers, imports, reuse, rad-export, KL scoring
- the (arch id, quant) family table and the recipe of record per model
- kernel/quantiser plugin authoring, encodings, build and checks
- architecture plugin authoring: declare, step, probe, lane and media rules
- rad-info/radbench/radtune and the shell harnesses
- the container contract, host prerequisites, readiness and restart triage

Also completes the dangling Related line on the frank-archon endpoint page.

serverAppConfigs-docs/LLM/frank-archon.md

@@ -655,5 +655,6 @@ vllm-radiance era (this table opens on 09-26; the era page claims 10-10).
 - Retired-era leftovers in-tree: `scripts/patches/glm53-*.patch`
   `scripts/patches/gpu_worker-kv-cap.patch` (fork archaeology; none applies byte-exact today).
 
-Related: [[frank-dragoon]] (the abliterated family), [[frank-zealot]],
----
+Related: [[frank-dragoon]] (the abliterated family), [[frank-zealot]], and the engine reference —
+[[Radiance Engine]], [[Radiance Serve Options]], [[Radiance Conversion]], [[Radiance Plugins]],
+[[Radiance Operations]].