feat(packaging): move the CLI into nexusos_cli and make the wheel self-sufficient

The CLI shipped from `management/`, which also holds desktop-only pieces (the
Tk control panel, the XFCE panel wiring, the shell wrappers). Packaging that
directory meant the wheel either dragged in tkinter or shipped a broken import.
Split it: `nexusos_cli/` is what the wheel ships and what `nexus`/`ncp`/
`nexusos` dispatch to, `management/` keeps the desktop half.

Alongside the move:

* hatch_build.py decides the interface/web/dist include at build time. dist/
  is gitignored, so a static force-include aborts `pip install -e .` on a
  fresh clone - before the reader reaches the `npm run build` step. Editable
  installs now skip a missing dist; wheels and sdists hard-error naming the
  command to run.
* synapse/proc_util.py gives frontend_manager and ncp process inspection and
  termination without psutil, which became an optional extra when the wheel
  landed. It routes around Windows having no signals, where os.kill(pid, 15)
  is an unblockable TerminateProcess rather than a polite request.
* nexusos_cli/monitor.py adds `ncp monitor`, an ASCII dashboard with no curses
  or rich dependency so it works in Termux, plain SSH and Windows Terminal.
  Collector and renderer are separate so tests feed fixtures, no stack needed.
* tests/test_packaging_deps.py fails the gate when synapse or nexusos_cli
  import a distribution pyproject does not declare, and when an optional
  dependency is imported at module scope instead of lazily.
* bin/check.sh now builds the wheel, twine-checks it, and asserts the compiled
  UI and seed playbooks are actually inside it. A wheel that builds but ships
  no dist/ serves a blank page, which only shows up after release.

tests/test_nexus_api.py moves to tests/ with the module it covers.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

management/__init__.py

@@ -1 +1,5 @@
-"""NexusOS command-line and desktop management helpers."""
+"""Desktop-only NexusOS management helpers (Tk control panel, XFCE panel).
+
+The portable CLI lives in the `nexusos_cli` package - that is what the
+wheel ships and what `ncp`/`nexus`/`nexusos` dispatch to.
+"""