[devcontainer] Align base image with production, fix Python venv and build tools (#17296)

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

.devcontainer/Dockerfile

@@ -1,4 +1,4 @@
-ARG BUILD_BASE_VERSION=2025.04.0
+ARG BUILD_BASE_VERSION=2026.06.1
 
 
 FROM ghcr.io/esphome/docker-base:debian-${BUILD_BASE_VERSION} AS base

.devcontainer/devcontainer.json

@@ -15,7 +15,6 @@
     // uncomment and edit the path in order to pass through local USB serial to the container
     // , "--device=/dev/ttyACM0"
   ],
-  "appPort": 6052,
   // if you are using avahi in the host device, uncomment these to allow the
   // devcontainer to find devices via mdns
   //"mounts": [
@@ -41,7 +40,11 @@
       ],
       "settings": {
         "python.languageServer": "Pylance",
-        "python.pythonPath": "/usr/bin/python3",
+        // Use the container's pre-provisioned venv (built by the Dockerfile, outside the
+        // bind-mounted workspace) rather than a ./venv that may leak in from the host and
+        // mismatch the container's Python. See .devcontainer/Dockerfile (esphome-venv).
+        "python.defaultInterpreterPath": "/home/esphome/.local/esphome-venv/bin/python",
+        "python.terminal.activateEnvironment": true,
         "pylint.args": [
           "--rcfile=${workspaceFolder}/pyproject.toml"
         ],

script/setup

@@ -4,7 +4,12 @@
 set -e
 
 cd "$(dirname "$0")/.."
-if [ ! -n "$VIRTUAL_ENV" ]; then
+if [ -n "$VIRTUAL_ENV" ]; then
+  # A virtual environment is already active (e.g. the devcontainer's pre-provisioned
+  # esphome-venv). Install into it rather than creating a ./venv in the workspace.
+  created_venv=false
+else
+  created_venv=true
   if [ -x "$(command -v uv)" ]; then
     uv venv --seed venv
   else
@@ -26,4 +31,10 @@ mkdir -p .temp
 
 echo
 echo
-echo "Virtual environment created. Run 'source venv/bin/activate' to use it."
+if [ "$created_venv" = true ]; then
+  echo "Virtual environment created at ./venv. Run 'source venv/bin/activate' to use it."
+else
+  echo "Dependencies installed into the active virtual environment:"
+  echo "  $VIRTUAL_ENV"
+  echo "It is already active in this shell, so no 'source venv/bin/activate' is needed."
+fi