Ship the reader wheels inside the package for offline install

A device with no internet could not set itself up: the auto-install needed
PyPI. The rdm6300 and pyserial wheels now ship inside the package, so first
start works with no network at all.

Both wheels are pure Python (py3-none-any / py2.py3-none-any), which is what
makes this possible - the same files work on armv7l, aarch64 and x86_64. This
is the difference from the workstation app's Files/repository cache, which
held aarch64 manylinux binaries and so could not be committed; that cache only
ever existed on the Pi devices.

- bundled_wheel_dir() locates them; ensure_dependencies() prefers them
  automatically, so the service needs no --wheel-dir.
- verify_wheels() checks SHA256SUMS before installing. A wheel that fails its
  checksum is refused rather than installed, then PyPI is tried, and if that is
  unreachable it reports exit 2 instead of proceeding unverified.
- local_wheel_missing() falls back to PyPI when the bundle does not cover a
  requirement, instead of attempting a --no-index install that must fail.
- An explicit --wheel-dir that is incomplete or unverified is called out, not
  silently swapped for PyPI.

Verified end to end: built wheel and sdist both contain the wheels; a venv
with no rdm6300 self-provisions with a dead proxy and no PIP_NO_INDEX; and a
tampered wheel is refused with nothing installed.

tests/test_bootstrap.py

@@ -7,6 +7,7 @@ clearly instead of crashing.
 
 import os
 import sys
+import tempfile
 
 SRC = os.path.join(
     os.path.dirname(os.path.dirname(os.path.abspath(__file__))), "src"
@@ -161,10 +162,11 @@ def test_no_install_flag_reports_manual_hint(monkeypatch):
 
 
 def test_wheel_dir_is_passed_through(monkeypatch):
+    """An explicit --wheel-dir that covers everything is used as given."""
     seen = {}
     monkeypatch.setattr(
         bootstrap, "missing_packages",
-        lambda packages=None: [] if seen.get("done") else [("x", "x")],
+        lambda packages=None: [] if seen.get("done") else [("x", "x>=1")],
     )
 
     def fake_install(requirements, wheel_dir=None, logger=None, timeout=300):
@@ -173,5 +175,27 @@ def test_wheel_dir_is_passed_through(monkeypatch):
         return True
 
     monkeypatch.setattr(bootstrap, "install", fake_install)
-    ensure_dependencies(wheel_dir="/opt/wheels")
-    assert seen["wheel_dir"] == "/opt/wheels"
+
+    with tempfile.TemporaryDirectory() as folder:
+        open(os.path.join(folder, "x-1.0-py3-none-any.whl"), "wb").close()
+        ensure_dependencies(wheel_dir=folder)
+        assert seen["wheel_dir"] == folder
+
+
+def test_incomplete_explicit_wheel_dir_is_flagged(monkeypatch):
+    """An unusable --wheel-dir should be called out, not silently ignored."""
+    seen = {}
+    monkeypatch.setattr(
+        bootstrap, "missing_packages",
+        lambda packages=None: [] if seen.get("done") else [("x", "x>=1")],
+    )
+
+    def fake_install(requirements, wheel_dir=None, logger=None, timeout=300):
+        seen["done"] = True
+        return True
+
+    monkeypatch.setattr(bootstrap, "install", fake_install)
+    lines = []
+    with tempfile.TemporaryDirectory() as folder:
+        ensure_dependencies(wheel_dir=folder, logger=lines.append)
+    assert any("you gave is incomplete" in line for line in lines)