ci(probe): temporary image build probe, not for main

The Dockerfile, .devcontainer and .cnb.yml named Rust 1.88, below the 1.89
workspace floor, and worked only because rustup fetched the toolchain named by
rust-toolchain.toml inside the image. They now name 1.100.0 (tags
rust:1.100.0-slim-bookworm and rust:1.100.0-bookworm return 200 on Docker Hub),
matching the pin RU-01 puts in rust-toolchain.toml so no second toolchain
downloads during the build.

Checks: release-workflows.test.js green (11 event cases, 13 hermetic checks).

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

.cnb.yml

@@ -48,7 +48,7 @@
     tags: cnb:arch:amd64
     cpus: 16
   docker:
-    image: rust:1.88-bookworm
+    image: rust:1.100.0-bookworm
   # codewhale-cnb-bridge GitHub App credentials from the CNB KeyStore
   # (codewhale.net/codewhale-ci-secrets, github-bridge.yml), injected as
   # environment variables. Values are never printed.
@@ -112,7 +112,7 @@
     tags: cnb:arch:amd64
     cpus: 16
   docker:
-    image: rust:1.88-bookworm
+    image: rust:1.100.0-bookworm
   stages:
     - name: install release dependencies
       script: |
@@ -163,7 +163,7 @@ main:
 $:
   tag_push:
     - docker:
-        image: rust:1.88-bookworm
+        image: rust:1.100.0-bookworm
       stages:
         - name: build linux x64 release assets (static)
           # The static full-LTO link can also outlive CNB's default no-output

.devcontainer/Dockerfile

@@ -1,4 +1,4 @@
-ARG RUST_VERSION=1.88
+ARG RUST_VERSION=1.100.0
 FROM rust:${RUST_VERSION}-slim-bookworm
 
 # Native DBus headers and pkg-config are required by libdbus-sys during

.devcontainer/devcontainer.json

@@ -4,7 +4,7 @@
     "context": "..",
     "dockerfile": "Dockerfile",
     "args": {
-      "RUST_VERSION": "1.88"
+      "RUST_VERSION": "1.100.0"
     }
   },
   "customizations": {

.github/workflows/ru08-image-probe.yml

@@ -0,0 +1,18 @@
+name: ru08-image-probe
+on:
+  push:
+    branches: ['ci/ru-08**']
+jobs:
+  image:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        platform: [linux/amd64, linux/arm64]
+    steps:
+      - uses: actions/checkout@v4
+      - uses: docker/setup-buildx-action@v3
+      - name: Build release Dockerfile
+        run: docker buildx build --platform ${{ matrix.platform }} -f Dockerfile --progress=plain . 
+      - name: Build devcontainer image
+        run: docker buildx build -f .devcontainer/Dockerfile --build-arg RUST_VERSION=1.100.0 --progress=plain .

Dockerfile

@@ -12,7 +12,7 @@
 # Or mount an env file:
 #   docker run --rm -it --env-file .env codewhale
 
-ARG RUST_VERSION=1.88
+ARG RUST_VERSION=1.100.0
 
 # ── Stage 1: Build ────────────────────────────────────────────────────
 FROM --platform=$BUILDPLATFORM rust:${RUST_VERSION}-slim-bookworm AS builder