dev-updater: build an app on the machine, install it on the phone

A Rust backend that discovers Android projects under configured roots,
builds one on request, and serves the APK over pinned TLS on a WireGuard
interface; an Android client that lists what is buildable, watches a build,
and installs the result. Enrolment carries the token and the CA, so the
phone trusts exactly the machine that issued it and nothing else.

`AGENTS.md` is the working guide and `README.md` the configuration
reference. The shared tunnel-and-TLS code lives in `vendor/wg-app-link`,
which ai-app uses too.

History before this point was squashed away, and a stale `config.json` went
with it: nothing had read that file since the config moved to RON outside
the checkout, and what it still held was one machine's absolute paths and
the names of projects on it.

run-tests.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+# Runs this repo's tests. Extra arguments are forwarded to `cargo test`,
+# e.g. `./run-tests.sh discover` to run just the discovery tests.
+#
+# Only `server/` has tests: it holds all the logic worth testing (APK
+# discovery, config round-tripping, staleness, the git read/pull/check
+# split, token gating, certificate generation), while the Android app is
+# UI over its HTTP API. Verifying the app means running it -- see the
+# README.
+set -eu
+cd "$(dirname "$0")/server"
+exec cargo test "$@"