fix(ci): install full shellspec directory tree, not just the binary

ShellSpec requires its lib/ directory alongside the shellspec binary.
Copying only the binary to /usr/local/bin breaks the relative path
lookup for shellspec.sh. Install the full tree to /usr/local/lib/shellspec
and symlink the binary.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: beadon

.github/workflows/test.yml

@@ -44,7 +44,8 @@ jobs:
           curl -fsSL -o /tmp/shellspec-dist.tar.gz "$SHELLSPEC_URL"
           echo "${SHELLSPEC_SHA256}  /tmp/shellspec-dist.tar.gz" | sha256sum --check --strict
           tar -xzf /tmp/shellspec-dist.tar.gz -C /tmp
-          sudo install -m 755 /tmp/shellspec/shellspec /usr/local/bin/shellspec
+          sudo cp -r /tmp/shellspec /usr/local/lib/shellspec
+          sudo ln -sf /usr/local/lib/shellspec/shellspec /usr/local/bin/shellspec
 
       - name: Run unit tests
         run: shellspec --shell busybox spec/unit/
@@ -67,7 +68,8 @@ jobs:
           curl -fsSL -o /tmp/shellspec-dist.tar.gz "$SHELLSPEC_URL"
           echo "${SHELLSPEC_SHA256}  /tmp/shellspec-dist.tar.gz" | sha256sum --check --strict
           tar -xzf /tmp/shellspec-dist.tar.gz -C /tmp
-          sudo install -m 755 /tmp/shellspec/shellspec /usr/local/bin/shellspec
+          sudo cp -r /tmp/shellspec /usr/local/lib/shellspec
+          sudo ln -sf /usr/local/lib/shellspec/shellspec /usr/local/bin/shellspec
 
       - name: Build OpenWrt test container
         # Pin by digest to prevent tag mutation attacks.