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/index.md

@@ -13,6 +13,20 @@ the endpoint's **Eras** table, and the numbers a retired era measured are gone.
 | [[frank-dragoon]] | The iGPU endpoint: live shape, every era with its rollback path, the laws it paid for, and the files that own it. |
 | [[frank-zealot]] | The RTX 3090 endpoint: live shape exactly as the env ships it, every era with its rollback path, and its card laws. |
 
+## Radiance engine reference
+
+| Page | Owns |
+|---|---|
+| [[Radiance Engine]] | The radiance inference engine: its shape, plugin model, container format, and how the reference pages fit together. |
+| [[Radiance Serve Options]] | Every radiance serve flag grouped by task, with its default and the law that decides when to move it. |
+| [[Radiance HTTP API]] | The HTTP surface radiance serves: endpoints, request fields, streaming, tools, and refusal rules. |
+| [[Radiance Conversion]] | Turning a checkpoint into a .rad container: rad-convert, the recipe language, quantisers, reuse and export. |
+| [[Radiance Model Families]] | Which radiance plugin claims which model family, and the conversion command and recipe of record for each. |
+| [[Radiance Plugins]] | Writing radiance kernel and quantiser plugins: the ABI, kernel rows, hooks, encodings, and the build path. |
+| [[Radiance Architecture Plugins]] | Writing a radiance architecture plugin: declaring weights, buffers, KV groups and ops, then issuing the step. |
+| [[Radiance Tools]] | The radiance inspection, measurement and tokeniser tools, with the flags and verdicts each one reports. |
+| [[Radiance Operations]] | Running a radiance server: the container contract, host prerequisites, readiness, ledgers and safe restarts. |
+
 ## Retired endpoints
 
 | Page | Owns |