test/hil: add stm32u083nucleo to pool and expose ~/bin on remote PATH

Add stm32u083nucleo to the active boards in tinyusb.json, flashed via the
stlink flasher (onboard ST-Link + STM32CubeProgrammer); ci's openocd build
has no STM32U0 flash driver. STM32_Programmer_CLI lives in ~/bin on ci,
which the remote `bash -s` shell in hil_ci.sh did not have on PATH, so add
$HOME/bin to its PATH export (matching the GHA runner .path). Verified
remote: 13/13 device tests pass on ci.lan.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

test/hil/tinyusb.json

@@ -455,6 +455,19 @@
                 "uid": "777632258",
                 "args": "-device STM32L476VG"
             }
+        },
+        {
+            "name": "stm32u083nucleo",
+            "uid": "300044000D5036394E373620",
+            "tests": {
+                "device": true,
+                "host": false,
+                "dual": false
+            },
+            "flasher": {
+                "name": "stlink",
+                "uid": "0668FF575457657187061314"
+            }
         }
     ],
     "boards-skip": [