add shop documentation and fix shop remove

CLAUDE.md

@@ -119,6 +119,20 @@ var v = a[]   // pop: v is 3, a is [1, 2]
 - `packages/` — core packages
 - `Makefile` — build system (`make` to rebuild, `make bootstrap` for first build)
 
+## Package Management (Shop CLI)
+
+When running locally with `./cell --dev`, these commands manage packages:
+
+```
+./cell --dev add <path>                    # add a package (local path or remote)
+./cell --dev remove <path>                 # remove a package (cleans lock, symlink, dylibs)
+./cell --dev build <path>                  # build C modules for a package
+./cell --dev test package <path>           # run tests for a package
+./cell --dev list                          # list installed packages
+```
+
+Local paths are symlinked into `.cell/packages/`. The build step compiles C files to `.cell/lib/<pkg>/<stem>.dylib`. C files in `src/` are support files linked into module dylibs, not standalone modules.
+
 ## Testing
 
 After any C runtime changes, run all three test suites before considering the work done: