let a stack compute its settings without make

A stack can now ship <name>.env and <name>.sh next to its compose files. The
hook is sourced with the tag helpers available, which is what the computing
.mk files of the catalogue were using make for: 29 of its 44 .mk files only
exist to build variables like the fabio tags.

Converting stack/host/fabio.mk by hand gives byte-identical output for the
route tag, and drops a trailing comma the make version left in the listener
list.

Also: APP_HOST and APP_URI are computed (the tag helpers build on them),
--color controls the escape codes rather than always emitting them, and
make test-portability runs the CLI under busybox ash and dash.

CHANGELOG.md

@@ -10,6 +10,10 @@
 - `myos ls`, `myos env`, `myos doctor` to inspect an installation
 - `install.sh`, and the catalogue is looked up beside the installation
 - agent skill in `skills/myos/`, contributor notes in `AGENTS.md`
+- stacks carry their settings in `<name>.env` and `<name>.sh` hooks, so the
+  catalogue no longer needs make to be installed
+- `--color always|never|auto`, and no colour when the output is piped
+- verified under the /bin/sh of Alpine (busybox) and Debian (dash)
 - the make engine still works and is still covered by the golden tests
 
 ## v1.1 - 2026-09-03