Document file system object content addressing

In addition:

- Take the opportunity to add a bunch more missing hyperlinks, too.

- Remove some glossary entries that are now subsumed by dedicated pages.
  We used to not be able to do this without breaking link fragments, but
  now we can, so pick up where we left off.

Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>

doc/manual/src/command-ref/nix-store/export.md

@@ -1,6 +1,6 @@
 # Name
 
-`nix-store --export` - export store paths to a Nix Archive
+`nix-store --export` - export store paths to a [Nix Archive]
 
 ## Synopsis
 
@@ -11,7 +11,7 @@
 The operation `--export` writes a serialisation of the specified store
 paths to standard output in a format that can be imported into another
 Nix store with `nix-store --import`. This is like `nix-store
---dump`, except that the NAR archive produced by that command doesn’t
+--dump`, except that the [Nix Archive (NAR)][Nix Archive] produced by that command doesn’t
 contain the necessary meta-information to allow it to be imported into
 another Nix store (namely, the set of references of the path).
 
@@ -19,6 +19,8 @@ This command does not produce a *closure* of the specified paths, so if
 a store path references other store paths that are missing in the target
 Nix store, the import will fail.
 
+[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
+
 {{#include ./opt-common.md}}
 
 {{#include ../opt-common.md}}