refactor: move firmware workspace under firmware

docs/src/index.md

@@ -12,6 +12,8 @@ Markdown.
 ## Index
 
 - New contributors should read [Getting started](getting-started.md).
+- Firmware source and its Rust workspace begin in `firmware/`; the desktop
+  application is a sibling project in `ground-suite/`.
 - 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
@@ -22,9 +24,11 @@ Markdown.
 
 ## Documentation conventions
 
-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.
+Documentation is centralized in `docs/src/`; individual crates and board
+directories do not carry README files. The top-level `firmware/README.md`
+only defines the firmware workspace boundary. Keep pages in Markdown, add each
+page to `SUMMARY.md`, and place commands beside the assumptions and safety
+boundary they depend on.
 
 The current configuration contract is intentionally deployment-specific. A
 SITL Quad-X profile is a bounded restart-only CBOR snapshot; F722 hardware