feat: relative mouse on the HID interface, and the verifier to prove it

The board now enumerates as a boot keyboard plus a relative mouse on the same
HID interface. The pointer is captured, never grabbed: Pointer Lock in the
page, so Esc (the browser's own, never forwarded) always frees it, and every
frame restates the whole button byte so a frame lost in the WiFi cannot leave
a button held. Losing the lock, the tab or the link runs the same release
funnel as a stuck key, and boot protocol or `mouse off` refuses mouse frames
with E11 rather than sending bytes a boot interface would misparse as keys.

src/mouse.h owns the report, src/output.h the queues and the funnel; the page,
relayctl.py and watch_target.py carry the button bits and the evdev decoding.
The verifier's own tables are pinned now — REL_WHEEL is 8, not 2, and the
first version guessed from the report's field order, so a working wheel looked
dead while the summary said no scroll happened.

LLM-Generated: true

tests/run_tests.sh

@@ -4,9 +4,10 @@
 #   tests/run_tests.sh          build and run every suite
 #   tests/run_tests.sh clean    remove the build directory
 #
-# The modules under test (src/keystate.h, src/proto.h, src/text.h, src/ws_codec.h,
-# src/sha1.h) have no Arduino or ESP-IDF dependency by design, so the exact code that
-# runs on the board is compiled and exercised here before anything is flashed.
+# The modules under test (src/keystate.h, src/proto.h, src/text.h, src/mouse.h,
+# src/output.h, src/ws_codec.h, src/sha1.h) have no Arduino or ESP-IDF dependency by
+# design, so the exact code that runs on the board is compiled and exercised here before
+# anything is flashed.
 #
 # A C++ compiler is not always installed on a workstation, so the runner picks one:
 #   $CXX                        if you set it, it wins
@@ -32,7 +33,7 @@ images=(
     "docker.io/library/gcc:14"
 )
 
-suites=(test_keystate test_proto test_text test_ws_codec)
+suites=(test_keystate test_proto test_text test_mouse test_output test_ws_codec)
 
 build_and_run() {
     local cxx="$1"