fix: use GITHUB_WORKSPACE env var instead of template in containers

${{ github.workspace }} template expands to host path at parse time,
but inside Docker containers the actual workspace path is different.
Use $GITHUB_WORKSPACE environment variable which is correct at runtime.

.github/workflows/check-getting-started.yml

@@ -180,17 +180,19 @@ jobs:
 
       # Build the template from within the SDK workspace context
       # Templates use workspace inheritance and can't be built standalone
+      # Note: Use $GITHUB_WORKSPACE env var, not ${{ github.workspace }} template
+      # because inside containers the template expands to host path which doesn't exist
       - name: Compile the template node
         run: |
           . "$HOME/.cargo/env"
-          cd ${{ github.workspace }}
+          cd "$GITHUB_WORKSPACE"
           cargo build --release -p ${{ matrix.package }}
         timeout-minutes: 120
 
       - name: Check that the binary is executable
         run: |
           . "$HOME/.cargo/env"
-          cd ${{ github.workspace }}
+          cd "$GITHUB_WORKSPACE"
           cargo run --release -p ${{ matrix.package }} -- --help
         timeout-minutes: 5
 
@@ -312,16 +314,18 @@ jobs:
 
       # Build the template from within the SDK workspace context
       # Templates use workspace inheritance and can't be built standalone
+      # Note: Use $GITHUB_WORKSPACE env var, not ${{ github.workspace }} template
+      # because inside containers the template expands to host path which doesn't exist
       - name: Compile the template node
         run: |
           . "$HOME/.cargo/env"
-          cd ${{ github.workspace }}
+          cd "$GITHUB_WORKSPACE"
           cargo build --release -p ${{ matrix.package }}
         timeout-minutes: 120
 
       - name: Check that the binary is executable
         run: |
           . "$HOME/.cargo/env"
-          cd ${{ github.workspace }}
+          cd "$GITHUB_WORKSPACE"
           cargo run --release -p ${{ matrix.package }} -- --help
         timeout-minutes: 5