docs: document configuration and diagnostics contracts

docs/src/index.md

@@ -14,6 +14,10 @@ Markdown.
 - New contributors should read [Getting started](getting-started.md).
 - Board work belongs under [Boards](boards/index.md).
 - The currently supported closed-loop simulation is [Host SITL](sitl.md).
+- [Configuration](configuration.md) distinguishes the current SITL profile
+  from immutable F722 board policy.
+- [Logs](logs.md) and [Errors](errors.md) describe the custom MAVLink
+  observability surface and its current safety scope.
 - Before submitting changes, follow [Development and verification](development.md).
 
 ## Documentation conventions
@@ -22,6 +26,7 @@ Documentation is centralized in `docs/src/`; source directories do not carry
 README files. Keep pages in Markdown, add each page to `SUMMARY.md`, and place
 commands beside the assumptions and safety boundary they depend on.
 
-`TODO(configuration)` marks a required configuration contract that has not
-been implemented. It is not permission for an operator to substitute runtime
-values or bypass an immutable build-time safety decision.
+The current configuration contract is intentionally deployment-specific. A
+SITL Quad-X profile is a bounded restart-only CBOR snapshot; F722 hardware
+selection remains immutable board policy. Neither is permission for an
+operator to substitute runtime values or bypass an immutable safety decision.