readme: update installation docs

Readme.org

@@ -12,19 +12,22 @@ Sex is statically typed, compiled general purpose language.
 First, get yourself a Chicken, then, some Chicken deps. You also will
 need a C compiler.
 
-** Install Chicken Eggs
-Tip: there's a way to make Chicken install eggs non-globally. You need
-to export ~CHICKEN_INSTALL_REPOSITORY~ and ~CHICKEN_REPOSITORY_PATH~
-environment variables. Refer to the documentation for more info:
-https://wiki.call-cc.org/man/5/Extension%20tools#changing-the-repository-location
-
-~chicken-install `cat dependencies.txt`~
+Eggs are installed into a project-local ~.eggs/~ repository; they do not
+touch the Chicken system repository.
 
 ** Compilation
 #+begin_src sh
   make
 #+end_src
 
+That installs pinned eggs from ~eggs.lock~ into ~.eggs/~ if needed, then
+builds ~sexc~. ~dependencies.txt~ is the unpinned request list. To
+refresh ~eggs.lock~ after changing it:
+
+#+begin_src sh
+  make deps-update
+#+end_src
+
 ** Static compilation
 The default ~CSC_FLAGS~ include ~-static~, so ~sexc~ does not need
 ~.eggs~ at runtime and ~make install~ stays relocatable. Chicken must