feat: add pipeline diagnostic script, viz/midi log recipes, reset-mcu recipe

- scripts/diagnostics/test-pipeline.py: full end-to-end test
- just diag-full: run pipeline diagnostic
- just viz-log/midi-log: watch service logs live
- just viz-stats/midi-stats: check counters
- just reset-mcu: reset MCU + reopen serial via router RPC
- just test-chord: send test MIDI chord locally
- just fix-perms: restore +x bits on all scripts

justfile

@@ -338,6 +338,74 @@ kconfig:
     @ssh {{SSH_OPTS}} "{{BOARD_USER}}@{{BOARD_HOST}}" "\
         zgrep -E 'CONFIG_USB_(GADGET|CONFIGFS|F_UAC1|F_MIDI|DWC3|F_ACC|F_SERIAL)' /proc/config.gz 2>/dev/null | awk -F= '{printf \"  %-45s %s\\n\", \$1, \$2}'"
 
+# Full pipeline diagnostic: test MIDI → viz → router → MCU → matrix
+diag-full:
+    python3 scripts/diagnostics/test-pipeline.py
+
+# Watch viz real-time log
+viz-log:
+    @ssh {{SSH_OPTS}} "{{BOARD_USER}}@{{BOARD_HOST}}" "journalctl -u led-matrix-viz -f -n 20"
+
+# Watch midi-bridge real-time log
+midi-log:
+    @ssh {{SSH_OPTS}} "{{BOARD_USER}}@{{BOARD_HOST}}" "journalctl -u midi-bridge -f -n 20"
+
+# Reset MCU via router RPC and reopen serial
+reset-mcu:
+    @ssh {{SSH_OPTS}} "{{BOARD_USER}}@{{BOARD_HOST}}" "\
+        python3 -c '
+import socket, msgpack, time
+s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+s.settimeout(5)
+s.connect(\"/var/run/arduino-router.sock\")
+p = msgpack.Packer()
+req = p.pack([0, 1, \"mon/reset\", []])
+s.sendall(req); s.recv(4096)
+req = p.pack([0, 2, \"\$/serial/close\", [\"/dev/ttyHS1\"]])
+s.sendall(req); s.recv(4096)
+req = p.pack([0, 3, \"\$/serial/open\", [\"/dev/ttyHS1\"]])
+s.sendall(req); s.recv(4096)
+s.close()
+print(\"MCU reset, serial reopened. Wait 20s for Bridge.begin()...\")
+'"
+
+# Check viz stats live
+viz-stats:
+    @ssh {{SSH_OPTS}} "{{BOARD_USER}}@{{BOARD_HOST}}" "cat /tmp/viz-stats.json"
+
+# Check midi-bridge stats live
+midi-stats:
+    @ssh {{SSH_OPTS}} "{{BOARD_USER}}@{{BOARD_HOST}}" "cat /tmp/midi-stats.json 2>/dev/null || echo '(no stats - bridge may be down)'"
+
+# Show all service status
+svc-status:
+    @ssh {{SSH_OPTS}} "{{BOARD_USER}}@{{BOARD_HOST}}" "\
+        for s in arduino-router midi-bridge pd-synth-onboard led-matrix-viz prometheus-exporter; do \
+            echo \"  \$s: \$(systemctl is-active \$s 2>/dev/null)\"; \
+        done"
+
+# Send test MIDI chord to viz (local test, no MIDI controller needed)
+test-chord:
+    @ssh {{SSH_OPTS}} "{{BOARD_USER}}@{{BOARD_HOST}}" "\
+        python3 -c '
+import socket, time
+s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+for note in [60, 64, 67, 72]:
+    s.sendto(b\"midi 144 %d 100;\" % note, (\"127.0.0.1\", 8082))
+    time.sleep(0.15)
+time.sleep(0.5)
+for note in [60, 64, 67, 72]:
+    s.sendto(b\"midi 128 %d 0;\" % note, (\"127.0.0.1\", 8082))
+    time.sleep(0.1)
+print(\"Sent C-E-G-C chord\")
+'"
+
+# Fix permissions on all scripts (run after clone/checkout)
+fix-perms:
+    @ssh {{SSH_OPTS}} "{{BOARD_USER}}@{{BOARD_HOST}}" "\
+        chmod +x {{REPO_DIR}}/scripts/*.py {{REPO_DIR}}/scripts/*.sh 2>/dev/null; \
+        echo 'Permissions fixed'"
+
 # Compile and flash the MCU sketch (LED matrix bridge) via SWD
 flash-sketch:
     @ssh {{SSH_OPTS}} "{{BOARD_USER}}@{{BOARD_HOST}}" "\