chore(tvix/docs): move daemon protocol to its own chapter

… and add an introductionary page at the root.

Change-Id: I89ce69a4221c332b7c0d99ac26b4e26bfd248341
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11806
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Reviewed-by: Brian Olsen <me@griff.name>

tvix/docs/src/SUMMARY.md

@@ -8,7 +8,8 @@
 - [Specification of the Nix Language](./language-spec.md)
 - [Nix language version history](./lang-version.md)
 - [Value Pointer Equality](./value-pointer-equality.md)
-- [Daemon protocol changelog](./nix-daemon/changelog.md)
-- [Daemon protocol logging](./nix-daemon/logging.md)
-- [Daemon protocol operations](./nix-daemon/operations.md)
-- [Daemon protocol serialization](./nix-daemon/serialization.md)
+- [Daemon Protocol](./nix-daemon/index.md)
+  - [Changelog](./nix-daemon/changelog.md)
+  - [Logging](./nix-daemon/logging.md)
+  - [Operations](./nix-daemon/operations.md)
+  - [Serialization](./nix-daemon/serialization.md)

tvix/docs/src/nix-daemon/index.md

@@ -0,0 +1,15 @@
+# Nix Daemon Protocol
+
+The Nix Daemon protocol is what's used to communicate with the `nix-daemon`,
+either on the local system (in which case the communication happens via a Unix
+domain socket), or with a remote Nix (in which this is tunneled over SSH).
+
+It uses a custom binary format which isn't too documented. The subpages here
+collect serve as an in-depth detail about some of the inner workings, data types
+etc.
+
+A first implementation of this exists in
+[griff/Nix.rs](https://github.com/griff/Nix.rs/tree/main).
+
+Work is underway to port / factor this out into reusable building blocks into
+the [nix-compat] crate.