Align CI with the validated Ubuntu support floor

Stop implying that one Ubuntu 3.11 unit lane validates the full Linux support surface Aman documents.\n\nSplit CI into an Ubuntu CPython 3.10/3.11/3.12 unit-package matrix, a portable install plus doctor smoke lane, and a packaging lane gated on both. Add a reproducible ci_portable_smoke.sh helper with fake systemctl coverage, and force the installer onto /usr/bin/python3 so the smoke path uses the distro-provided GI and X11 Python packages it is meant to validate.\n\nUpdate the README, release/distribution docs, and Debian metadata to distinguish the automated Ubuntu CI floor from broader manual GA signoff families, and add the missing AppIndicator introspection package to the Ubuntu/Debian dependency lists.\n\nValidate with python3 -m unittest discover -s tests -p 'test_*.py', python3 -m py_compile src/*.py tests/*.py, and bash -n scripts/ci_portable_smoke.sh. The full xvfb-backed smoke could not be run locally in this sandbox because xvfb-run is unavailable.

docs/persona-and-distribution.md

@@ -50,7 +50,10 @@ For X11 GA, Aman supports:
 - Runtime dependencies installed from the distro package manager.
 - `systemd --user` as the supported daily-use path.
 - `aman run` as the foreground setup, support, and debugging path.
-- Representative validation across Debian/Ubuntu, Arch, Fedora, and openSUSE.
+- Automated validation floor on Ubuntu CI: CPython `3.10`, `3.11`, and `3.12`
+  for unit/package coverage, plus portable install and `aman doctor` smoke with
+  Ubuntu system `python3`.
+- Manual GA signoff families: Debian/Ubuntu, Arch, Fedora, openSUSE.
 - The recovery sequence `aman doctor` -> `aman self-check` ->
   `journalctl --user -u aman` -> `aman run --verbose`.