manual: Contributing -> Development, Hacking -> Compiling

what's currently called "hacking" are really instructions for setting up
a development environment and compiling from source. we have
a contribution guide in the repo (which rightly focuses on GitHub
workflows), and the material in the manual is more about working
on the code itself.

we may want to reorganise this in the future, and bring
contributor-oriented information closer to the code, but for now let's
stick to more accurate names to ease navigation.

README.md

@@ -20,8 +20,7 @@ Information on additional installation methods is available on the [Nix download
 
 ## Building And Developing
 
-See our [Hacking guide](https://nixos.org/manual/nix/unstable/contributing/hacking.html) in our manual for instruction on how to
-to set up a development environment and build Nix from source.
+Refer to [compilation guide in the manual](https://nixos.org/manual/nix/unstable/contributing/hacking.html) for instruction on how to to set up a development environment and build Nix from source.
 
 ## Additional Resources
 

doc/manual/src/SUMMARY.md.in

@@ -102,12 +102,12 @@
   - [Serving Tarball Flakes](protocols/tarball-fetcher.md)
   - [Derivation "ATerm" file format](protocols/derivation-aterm.md)
 - [Glossary](glossary.md)
-- [Contributing](contributing/contributing.md)
-  - [Hacking](contributing/hacking.md)
+- [Development](contributing/contributing.md)
+  - [Compiling](contributing/hacking.md)
   - [Testing](contributing/testing.md)
-  - [Experimental Features](contributing/experimental-features.md)
   - [CLI guideline](contributing/cli-guideline.md)
   - [C++ style guide](contributing/cxx.md)
+  - [Experimental Features](contributing/experimental-features.md)
 - [Release Notes](release-notes/release-notes.md)
   - [Release X.Y (202?-??-??)](release-notes/rl-next.md)
   - [Release 2.18 (2023-09-20)](release-notes/rl-2.18.md)

doc/manual/src/contributing/contributing.md

@@ -1 +1,8 @@
-# Contributing
+# Development
+
+Nix is developed on GitHub.
+Check the [contributing guide](https://github.com/NixOS/nix/blob/master/CONTRIBUTING.md) if you want to get involved.
+
+This chapter is a collection of guides for making changes to the code.
+
+If you're not sure where to start, try to [compile Nix from source](./hacking.md).

doc/manual/src/contributing/hacking.md

@@ -1,7 +1,7 @@
-# Hacking
+# Compiling Nix
 
-This section provides some notes on how to hack on Nix. To get the
-latest version of Nix from GitHub:
+This section provides some notes on how to start hacking on Nix.
+To get the latest version of Nix from GitHub:
 
 ```console
 $ git clone https://github.com/NixOS/nix.git