feat(freebsd): full FreeBSD 15.0 compatibility

- board: detect cuaU* serial ports in fallback scanner, filter .init/.lock nodes
- board: fall through to OS scan when arduino-cli returns empty (serial-discovery
  uses unsupported Linux syscalls on FreeBSD)
- board: recognize cuaU* port names as USB in is_usb()
- upload.sh: fix silent exit under set -euo pipefail when vid_pid grep finds
  nothing (|| true on LOCAL_PORT and LOCAL_VID_PID greps)
- upload.sh: add cuaU to auto-detect port pattern
- doctor: detect dialer and operator group membership, offer --fix for both
- doctor: detect avr-size installed but not on PATH, offer --fix to add to
  shell rc file via detect_shell_rc()
- doctor: context-aware hardware section (suppress misleading messages when
  groups not yet applied)
- doctor: FreeBSD-specific troubleshooting hints throughout
- devices: suppress arduino-cli board detection section on FreeBSD (broken
  due to serial-discovery syscall issues)
- devices: always show USB hub tip on FreeBSD
- devices: FreeBSD-specific troubleshooting checklist with sequential numbering
  on all platforms

templates/basic/upload.sh

@@ -39,8 +39,29 @@ toml_get() {
 }
 
 toml_array() {
-    (grep "^$1 " "$CONFIG" 2>/dev/null || true) | head -1 \
-        | sed 's/.*\[//; s/\].*//; s/"//g; s/,/ /g' | tr -s ' '
+    # Handles both single-line:  key = ["a", "b"]
+    # and multiline:             key = [
+    #                                "a",
+    #                                "b",
+    #                            ]
+    awk -v key="$1" '
+        $0 ~ ("^" key " *= *\\[") {
+            collecting = 1
+            buf = $0
+            if (index($0, "]") > 0) { collecting = 0 }
+        }
+        collecting && NR > 1 { buf = buf " " $0 }
+        collecting && index($0, "]") > 0 && NR > 1 { collecting = 0 }
+        !collecting && buf != "" {
+            gsub(/.*\[/, "", buf)
+            gsub(/\].*/, "", buf)
+            gsub(/"/, "", buf)
+            gsub(/,/, " ", buf)
+            print buf
+            buf = ""
+            exit
+        }
+    ' "$CONFIG" | tr -s " "
 }
 
 toml_section_get() {
@@ -195,7 +216,7 @@ if [[ -z "$PORT" ]]; then
         PORT=$(arduino-cli board list 2>/dev/null \
             | grep -i "serial" \
             | awk '{print $1}' \
-            | grep -E 'ttyUSB|ttyACM|COM' \
+            | grep -E 'ttyUSB|ttyACM|cuaU|COM' \
             | head -1)
 
         if [[ -z "$PORT" ]]; then