fix(ci): checkout apcore spec into workspace-internal path

GitHub Actions requires checkout paths to be under the workspace.
Changed from ../apcore to .apcore-spec and pass APCORE_SPEC_REPO
env var so conformance tests find the fixtures.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Author: tercel

.github/workflows/ci.yml

@@ -26,7 +26,7 @@ jobs:
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
           repository: aiperceivable/apcore
-          path: ../apcore
+          path: .apcore-spec
 
       - name: Install Rust toolchain
         uses: dtolnay/rust-toolchain@stable
@@ -64,6 +64,8 @@ jobs:
 
       - name: Run tests
         run: cargo test --all-features
+        env:
+          APCORE_SPEC_REPO: ${{ github.workspace }}/.apcore-spec
 
       - name: Build examples
         run: cargo build --examples