Use Ubuntu 25.10 in CI

We still need gtk4-layer-shell-dev, which is not available in Ubuntu
24.04.

I would have preferred to define an environment variable rather than
duplicating `image: ubuntu:25.10` everywhere, but those aren't supported
in the `container` field.

.github/workflows/ci.yml

@@ -27,16 +27,20 @@ jobs:
   build:
     name: Build
     runs-on: ubuntu-latest
+    container:
+      image: ubuntu:25.10
     steps:
+      - name: Install git and dependencies
+        run: |
+          apt-get update
+          apt-get install -y git curl ${{ env.SYSTEM_DEPS }}
+
       - uses: actions/checkout@v4
 
-      - name: Install system dependencies
-        run: |
-          sudo apt-get update
-          sudo apt-get install -y ${{ env.SYSTEM_DEPS }}
-
       - name: Setup Rust toolchain
-        uses: dtolnay/rust-toolchain@stable
+        run: |
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+          echo "$HOME/.cargo/bin" >> $GITHUB_PATH
 
       - name: Cache cargo registry and build
         uses: actions/cache@v4
@@ -50,21 +54,27 @@ jobs:
             ${{ runner.os }}-cargo-
 
       - name: Build
-        run: cargo build --all-targets
+        run: |
+          . "$HOME/.cargo/env"
+          cargo build --all-targets
 
   test:
     name: Test
     runs-on: ubuntu-latest
+    container:
+      image: ubuntu:25.10
     steps:
+      - name: Install git and dependencies
+        run: |
+          apt-get update
+          apt-get install -y git curl ${{ env.SYSTEM_DEPS }}
+
       - uses: actions/checkout@v4
 
-      - name: Install system dependencies
-        run: |
-          sudo apt-get update
-          sudo apt-get install -y ${{ env.SYSTEM_DEPS }}
-
       - name: Setup Rust toolchain
-        uses: dtolnay/rust-toolchain@stable
+        run: |
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+          echo "$HOME/.cargo/bin" >> $GITHUB_PATH
 
       - name: Cache cargo registry and build
         uses: actions/cache@v4
@@ -78,23 +88,28 @@ jobs:
             ${{ runner.os }}-cargo-
 
       - name: Run tests
-        run: cargo test --all-targets
+        run: |
+          . "$HOME/.cargo/env"
+          cargo test --all-targets
 
   lint:
     name: Clippy
     runs-on: ubuntu-latest
+    container:
+      image: ubuntu:25.10
     steps:
+      - name: Install git and dependencies
+        run: |
+          apt-get update
+          apt-get install -y git curl ${{ env.SYSTEM_DEPS }}
+
       - uses: actions/checkout@v4
 
-      - name: Install system dependencies
-        run: |
-          sudo apt-get update
-          sudo apt-get install -y ${{ env.SYSTEM_DEPS }}
-
       - name: Setup Rust toolchain
-        uses: dtolnay/rust-toolchain@stable
-        with:
-          components: clippy
+        run: |
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+          rustup component add clippy
+          echo "$HOME/.cargo/bin" >> $GITHUB_PATH
 
       - name: Cache cargo registry and build
         uses: actions/cache@v4
@@ -108,4 +123,6 @@ jobs:
             ${{ runner.os }}-cargo-
 
       - name: Run Clippy
-        run: cargo clippy --all-targets -- -D warnings
+        run: |
+          . "$HOME/.cargo/env"
+          cargo clippy --all-targets -- -D warnings