build: add Eask, test harness, and dev tooling

I brought the skeleton up to a working package baseline (Phase 0 in the design spec). Eask defines the package and its dev deps. A root Makefile delegates test targets to tests/Makefile and adds compile, coverage, lint, doctor, and clean, matching the layout the other packages use.

deps installs both halves DUET needs: the Emacs Lisp deps via eask, and the transport CLIs (rsync, rclone, lftp, unison) via the system package manager, so a contributor's environment is ready before the code that shells out to them.

make complexity runs a small homegrown McCabe branch counter (scripts/duet-complexity.el). No off-the-shelf tool measures Emacs Lisp: lizard doesn't support it and codemetrics is an interactive overlay, so DUET owns one. The counting is pure and covered by Normal/Boundary/Error tests. The budget is soft and the target is advisory.

The ERT harness (bootstrap, check-deps, per-file undercover coverage) and a smoke test prove the loop works end to end.

1 files changed, 36 insertions, 0 deletions

diff --git a/tests/test-duet-smoke.el b/tests/test-duet-smoke.el
new file mode 100644
index 0000000..a101dd2
--- /dev/null
+++ b/tests/test-duet-smoke.el
@@ -0,0 +1,36 @@
+;;; test-duet-smoke.el --- Harness smoke test for duet -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2026 Craig Jennings
+
+;; Author: Craig Jennings <c@cjennings.net>
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Plumbing-proof smoke test: confirms the harness loads the package and the
+;; entry command is defined.  Behavior coverage lives in the per-area test
+;; files added by later phases.
+
+;;; Code:
+
+(require 'test-bootstrap (expand-file-name "test-bootstrap.el"))
+
+(ert-deftest test-duet-smoke-feature-loaded ()
+  "The package source loads and defines its entry command."
+  (should (featurep 'duet))
+  (should (commandp 'duet)))
+
+(provide 'test-duet-smoke)
+;;; test-duet-smoke.el ends here