container builds: opt-in extension deps via OPENCLAW_EXTENSIONS build arg (#32223)

* Docker: opt-in extension deps via OPENCLAW_EXTENSIONS build arg

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: sallyom <somalley@redhat.com>

* CI: clarify extension smoke scope

* Tests: allow digest-pinned multi-stage FROM lines

* Changelog: note container extension preinstall option

---------

Signed-off-by: sallyom <somalley@redhat.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Vincent Koc <vincentkoc@ieee.org>

docs/install/docker.md

@@ -60,6 +60,7 @@ Optional env vars:
 
 - `OPENCLAW_IMAGE` — use a remote image instead of building locally (e.g. `ghcr.io/openclaw/openclaw:latest`)
 - `OPENCLAW_DOCKER_APT_PACKAGES` — install extra apt packages during build
+- `OPENCLAW_EXTENSIONS` — pre-install extension dependencies at build time (space-separated extension names, e.g. `diagnostics-otel matrix`)
 - `OPENCLAW_EXTRA_MOUNTS` — add extra host bind mounts
 - `OPENCLAW_HOME_VOLUME` — persist `/home/node` in a named volume
 - `OPENCLAW_SANDBOX` — opt in to Docker gateway sandbox bootstrap. Only explicit truthy values enable it: `1`, `true`, `yes`, `on`
@@ -320,6 +321,31 @@ Notes:
 - If you change `OPENCLAW_DOCKER_APT_PACKAGES`, rerun `docker-setup.sh` to rebuild
   the image.
 
+### Pre-install extension dependencies (optional)
+
+Extensions with their own `package.json` (e.g. `diagnostics-otel`, `matrix`,
+`msteams`) install their npm dependencies on first load. To bake those
+dependencies into the image instead, set `OPENCLAW_EXTENSIONS` before
+running `docker-setup.sh`:
+
+```bash
+export OPENCLAW_EXTENSIONS="diagnostics-otel matrix"
+./docker-setup.sh
+```
+
+Or when building directly:
+
+```bash
+docker build --build-arg OPENCLAW_EXTENSIONS="diagnostics-otel matrix" .
+```
+
+Notes:
+
+- This accepts a space-separated list of extension directory names (under `extensions/`).
+- Only extensions with a `package.json` are affected; lightweight plugins without one are ignored.
+- If you change `OPENCLAW_EXTENSIONS`, rerun `docker-setup.sh` to rebuild
+  the image.
+
 ### Power-user / full-featured container (opt-in)
 
 The default Docker image is **security-first** and runs as the non-root `node`

docs/install/podman.md

@@ -32,6 +32,11 @@ By default the container is **not** installed as a systemd service, you start it
 
 (Or set `OPENCLAW_PODMAN_QUADLET=1`; use `--container` to install only the container and launch script.)
 
+Optional build-time env vars (set before running `setup-podman.sh`):
+
+- `OPENCLAW_DOCKER_APT_PACKAGES` — install extra apt packages during image build
+- `OPENCLAW_EXTENSIONS` — pre-install extension dependencies (space-separated extension names, e.g. `diagnostics-otel matrix`)
+
 **2. Start gateway** (manual, for quick smoke testing):
 
 ```bash