Default to local builds for template portability

Switch devcontainer.json from prebuilt GHCR image to local builds as
the default. This ensures the template works out of the box for forks
and new projects without depending on a pre-existing GHCR image.

The prebuilt image is preserved as a commented-out option with
instructions in the README for enabling it, including the requirement
to make the GHCR package public (private by default).

Author: blooop

.devcontainer/devcontainer.json

@@ -1,23 +1,20 @@
 {
     "name": "python_template",
 
-    // Prebuilt image from GHCR (built by .github/workflows/devcontainer.yml)
-    // Features (including claude-code) are baked into this image.
-    "image": "ghcr.io/blooop/python_template/devcontainer:latest",
+    "build": {
+        "dockerfile": "Dockerfile",
+        "context": ".."
+    },
+    "features": {
+        "./claude-code": {},
+        "ghcr.io/devcontainers/features/docker-in-docker:2": {},
+        "ghcr.io/devcontainers/features/common-utils:2": {}
+    },
 
-    // To build locally instead of using the prebuilt image, comment out "image" above
-    // and uncomment the "build" and "features" blocks below:
-    // "build": {
-    //     "dockerfile": "Dockerfile",
-    //     "context": ".."
-    // },
-    // "features": {
-    //     "./claude-code": {},
-    //     "ghcr.io/devcontainers/features/docker-in-docker:2": {},
-    //     "ghcr.io/devcontainers/features/common-utils:2": {},
-    //     "ghcr.io/anthropics/devcontainer-features/claude-code:1.0": {},
-    //     "ghcr.io/jsburckhardt/devcontainer-features/codex:latest": {}
-    // },
+    // To use a prebuilt image instead of building locally (faster startup),
+    // comment out "build" and "features" above, uncomment "image" below,
+    // and ensure the GHCR package is public (see README).
+    // "image": "ghcr.io/blooop/python_template/devcontainer:latest",
 
     "initializeCommand": ".devcontainer/claude-code/init-host.sh",
     "customizations": {

README.md

@@ -57,21 +57,20 @@ source .claude/activate.sh
 
 See [.claude/README.md](.claude/README.md) for detailed information about the Claude Code configuration.
 
-# Devcontainer Prebuilt Image
+# Devcontainer
 
-This template includes a CI workflow (`.github/workflows/devcontainer.yml`) that automatically builds and pushes a devcontainer image to GitHub Container Registry (GHCR) whenever `.devcontainer/` files change on `main`.
+By default, the devcontainer builds locally from `.devcontainer/Dockerfile`. This works out of the box for all users, including forks and projects created from this template.
 
-The main `.devcontainer/devcontainer.json` references this prebuilt image to avoid slow local builds:
+## Switching to a prebuilt image (optional)
 
-```json
-"image": "ghcr.io/blooop/python_template/devcontainer:latest"
-```
-
-## GHCR Package Visibility
+A CI workflow (`.github/workflows/devcontainer.yml`) automatically builds and pushes a devcontainer image to GHCR whenever `.devcontainer/` files change on `main`. To use it for faster startup:
 
-**GHCR packages are private by default.** After the first CI push, you must manually make the package public or users (and tools like DevPod) will get a `MANIFEST_UNKNOWN` error when trying to pull the image.
+1. Edit `.devcontainer/devcontainer.json`: comment out the `"build"` and `"features"` blocks, uncomment the `"image"` line
+2. Update the image reference to match your repo: `ghcr.io/<owner>/<repo>/devcontainer:latest`
+3. Push to `main` and wait for the CI workflow to complete
+4. **Make the GHCR package public** (see below) — GHCR packages are private by default and will fail with `MANIFEST_UNKNOWN` otherwise
 
-### Making the package public
+### Making the GHCR package public
 
 **Option 1: GitHub Web UI**
 
@@ -90,10 +89,6 @@ gh auth refresh -s write:packages
 gh api --method PATCH /user/packages/container/<repo>%2Fdevcontainer -f visibility=public
 ```
 
-## Falling back to local builds
-
-If the prebuilt image is unavailable, you can switch to local builds by editing `.devcontainer/devcontainer.json`: comment out the `"image"` line and uncomment the `"build"` and `"features"` blocks.
-
 # Github setup
 
 There are github workflows for CI, codecov and automated pypi publishing in `ci.yml` and `publish.yml`.